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Nobadays
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# Posted: 15 Jul 2024 02:11pm
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A lot of smart guys on here so guessing someone might be able to help! I've been posting on a Class B forum but the suggestions and directions are kind of all over the place. Here is what I am puzzling over. Kind of long...
My 2000 Pleasure-Way Excel TD currently has 2 x grp24 lead acid batteries. I want to convert to lithium - LiTime makes a grp24/100ah with cold temp cut-off that should be ideal. I know I will need to change the current "converter" as it cannot be switched to charge lithium when on shower power or generator. I will also have to replace the battery isolator and herein lies my quandary.
The current battery isolator is a Sure Power 1202. It only has 3 terminals; Alternator input, Chassis Battery and House Battery. The plan is to replace it with the Li-BIM 225 designed for charging lithium, but in addition to the House/Chassis it includes; Ignition, ground and Sig terminals. But no alternator input terminal.
Obviously House, Chassis, Ground are straightforward. Wiring diagrams I've found show the ignition terminal to any power source only energized when the ignition is on. The "Sig" is for a momentary switch to connect house to chassis I guess in case you have run the Chassis Battery down.
The Li-BIM doesn't seem to have any input from the alternator.
The Li-BIM is supposed to replace a regular battery isolator as it will both regulate the charge to the House lithium battery - by only allowing 15 minutes of charge/20 minutes cooling so the alternator doesn't burn up, and it monitors charge to the Chassis LA battery to charge it properly as well. Apparently it plays well with both chemistries.
I have looked at wiring diagrams... apparently not the right ones... and I just can't figure how the BIM is fed the alternator output, or if it even is. If not.... well how would it regulate charging? I'm stumped!
The other option may be a DC to DC charger to manage the input to the lithium house batteries? But where to put it... just before the battery? Just after the current isolator?
Anyone done anything similar and can help?
Sure Power diagram
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BIM diagram
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paulz
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# Posted: 15 Jul 2024 02:50pm
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Whew, got me, I’m still trying to figure out gcranks inverter transfer system. I did just mess with the old Chevy alternator though, and the output terminal has battery voltage all the time (key off),which naturally jumps up to 14 when it’s running.
Old news I’m sure but I’ll be following along. You’re keeping a FLA for engine starting?
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travellerw
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# Posted: 15 Jul 2024 03:24pm
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I'm not familiar with that device, but based on the diagrams and the manual here is what I think.
You connect the alternator to the starter battery. Then the BIM connects the starter battery and the house battery during its charging regiem (according to the manual this is done via a "sliding contact"). It also works in reverse and allows shore power to charge the starting battery when in a campground (which would be very limited as everything should be floating at that point).
Now as to your charger/converter, you may not need to change it. It really depends on the documentation of the Li-time batteries. Also most charger/converters have a potentiometer on them somewhere that allows changing the charging voltage. If you can change the voltage to within spec for the batteries, then no need to change it.
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Nobadays
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# Posted: 15 Jul 2024 05:21pm - Edited by: Nobadays
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Quoting: paulz You’re keeping a FLA for engine starting?
Yes. I'm getting input that probably a DC to DC charger may be the way to go.
Edit.... I could then eliminate the battery isolator as the DC to DC charger replaces ithat.
I have a query in to the Pleasure-Way forum as well. Somebody has done this before me!
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Nobadays
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# Posted: 15 Jul 2024 05:41pm
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Quoting: travellerw You connect the alternator to the starter battery.
I have yet to download a manual for this thing but that was my assumption... I prefer not to assume!
So if this is indeed the case, the chassis battery and alternator output could be put on the same terminal on the BIM. I say that because where the wires connect is really the only difference. If I lengthened the alternator output wire and ran it to the chassis battery first, I'm just going to turn around and run another wire from the chassis battery back to the BIM. Hmmm.
Quoting: travellerw Now as to your charger/converter, you may not need to change it.
Interesting. At 24 years old I presumed it could not be capable of charging lithium, but maybe if it is adjustable! I am going to try to dig into the compartment where it is housed later today... not an easy task... I'll get the info off it and see if I can download a manual.
Thank you!
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travellerw
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# Posted: 15 Jul 2024 05:48pm
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Quoting: Nobadays Yes. I'm getting input that probably a DC to DC charger may be the way to go.
DC to DC will work as well, not sure one or the other is better.
I have done MANY conversions on boats which is very similar to an RV. Once piece of advice I would offer.
If you don't absolutely NEED to charge you Li batts with the alternator, then DON'T.
Removing that simplifies everything SOOOO much. Even with DC to DC chargers or battery isolators I have still seen alternators burn up. To do it right, you really need a controlled alternator with a temperature probe. Even if you don't burn them up, the belt dust becomes an issue (and a maintenance item as you need to replace them WAY more often). At least V-belts, serpentine work much better.
If most of your camping is at RV parks with power, or even if you have a generator, then there is really no need to charge off the alternator. Leave home with your batts charged and plug in when you get there.
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travellerw
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# Posted: 15 Jul 2024 05:55pm
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Quoting: Nobadays Interesting. At 24 years old I presumed it could not be capable of charging lithium, but maybe if it is adjustable! I am going to try to dig into the compartment where it is housed later today... not an easy task... I'll get the info off it and see if I can download a manual.
Another option is to crank up the voltage, then put a charge controller between the converter and the batteries. The converter voltage must remain at least .2V higher than the charge controller settings, otherwise the charge controller will complain about input voltage too low.
However, this route can be expensive (60A charge controllers aren't cheap) and it adds another point of failure.
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Nobadays
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# Posted: 15 Jul 2024 07:26pm
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Quoting: travellerw If you don't absolutely NEED to charge you Li batts with the alternator, then DON'T
I'm beginning to wonder if this isn't the best advice. We don't go to RV parks often but the van is usually plugged in at home. We boondock more often than not. If I have 2 x 100ah lifepo4 batteries for the house, they would last a long time I'm thinking. We have a portable 75w solar panel we use currently to charge our batteries while boondocking. It has an ultra-cheap scc on it but I could change that out for a good one capable of properly charging the lithium.
Not sure what direction I'll end up going.
Thanks!
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ICC
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# Posted: 15 Jul 2024 08:12pm - Edited by: ICC
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I had a special separate HD alternator made for external regulation and a Wakefield regulator on my bus/rv. It was super, loads of output if needed but not inexpensive. Worth it for the size of the system though.
On my present campervan I elected to use a Victron DC-DC charger, 15 amp to limit the current draw from the alternator. I have rooftop solar and a Honda EU2200 with a Victron 120 VAC charger as well. I almost did not bother with the DC-DC.
Both of the Victron chargers can be programmed for LFP use just like their MPPT solar chargers.
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gcrank1
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# Posted: 15 Jul 2024 09:35pm - Edited by: gcrank1
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We have used 12v 'marine/rv' bats for cabin and rv's since the mid '80's, then a couple years ago got the 2x 100ah LFP's for the cabin (had by then given up rv'ing).
I admit to some fear of damaging my marvelous LFP's, so I charge at home where I can keep an eye on things. They charge So much faster than LA!
My methodology with LA was to use only the top 25-30%, the LFP is so energy dense that I get 3x the amp hours out of each than a 100ah LA. And I don't have to recharge the LFP asap!
If you have been used to using the LA to 50% (and slowly killing them) then you will get almost 2x from LFP. It's pretty much mathematical.
Ive thought about getting a DC2DC charger for my utility SUV we take to the cabin to charge an LFP in transit but I haven't really needed it.
FWIW, I recharge off my home power supply at 14.0ish volts and take the bat to 13.6-13.8 (then settle back to 13.3 after a rest). The 14.6 charge voltage for LFP I often see in chargers is Too High for My comfort.
What Id do if still RV'ing:
I suggest you give the LFP's a trial run without charging hooked up (unless where grid power is available and you can use an LFP friendly charger) and find out how it works out. But do take a small generator off-grid as back up so you aren't left hanging. Whenever the gen runs have the 120vac charger hooked up and charging the bat. This puts you in control of the 'charging curve'.
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Nobadays
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# Posted: 15 Jul 2024 10:29pm
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Quoting: ICC On my present campervan I elected to use a Victron DC-DC charger, 15 amp to limit the current draw from the alternator.
Using such a low amperage DC-DC charger might help eliminate the excessive alternator/belt wear that travellerw was cautioning about.
We already have the converter/charger in the van so I think to avoid problems with the existing electrical system I will replace it with one that is lithium friendly. Rather than just using a 120v AC charger.
travellerw mentioned that I might be able to adjust the output from the current converter/charger, a Manatee model 7445, but everything I can find on my searches says this is an out dated C/C and cannot be made to work with lithium. I think it might be 3 stage and not adjustable and not switchable to constant output.
I might try to remove the house output wire from the current isolator and see if everything works... except charging the house batteries. If so that might shed some light.
Thanks guys!
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Nobadays
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# Posted: 15 Jul 2024 10:49pm
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BTW.... the reason I'm looking at this conversion now is because of a shorted positive terminal on one of my house batteries that burned up ~3' of all 4 positive wires attached to that terminal.
This was brought on by a catastrophic rear tire failure @65mph on a narrow two lane road with no shoulders. I was fortunately able to keep the van under control and got it stopped and limped to a close by driveway so I could get off the roadway. When the tire blew (my wife is pretty sure we ran over something in the road a few miles back) about a 3' section beat the he!! Out of the bottom of the battery compartment knocking the door off and bending the bottom of the compartment slightly. Also bent the tailpipe nearly in two.
Though it wasn't immediate evident, we believe one of the batteries must have momentarily hit the top of the compartment breaking/or compromising the positive terminal. We had DC power that night and the next day, but after driving the 23 miles up our horribly washboard road all DC was out. When I pulled out the battery tray that terminal was barely connected to the battery and sparked when moved. Lots of molten lead and, as I said plenty of burned wiring. The one battery is toast, the other surprisingly is still charged up.
Headed into town Wednesday to get new tires and butt end splices and lugs I ordered to repair the wires. It could have been worse, it could have burned back further or burned the whole van down.
Once I get the wires repaired I can do some experimenting to find out what is necessary and what can be removed/replaced to charge lithium.
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travellerw
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# Posted: 15 Jul 2024 10:56pm
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Quoting: Nobadays travellerw mentioned that I might be able to adjust the output from the current converter/charger, a Manatee model 7445, but everything I can find on my searches says this is an out dated C/C and cannot be made to work with lithium. I think it might be 3 stage and not adjustable and not switchable to constant output.
A quick googling shows that is just a dumb single stage one voltage charger (13.6V). Look for a hole with a POT, or you may have to remove the cover. I'm willing to bet you can adjust the voltage (or how would they set it at the factory).
HOWEVER.. If you aren't looking to pinch pennies, then its probably a great idea to replace it. Victron makes some really nice Inverter/chargers with built in auto switch. That is a whole new can of worms though.
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gcrank1
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# Posted: 15 Jul 2024 11:41pm - Edited by: gcrank1
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13.6v wouldn't be bad for lfp, easy on it actually, but a bit slow on recharge. The working voltage of lfp is about 13.0-13.2+, a rather narrow window but Long lasting in each 'tenth'. Ive charged at 13.6 with my power supply in getting used to how they work. My current setting of 14.0ish gives me a faster recharge without stressing the bats, but Im monitoring the recharge to disconnect manually.
What any of these 'chargers' being discussed wont do is Stop when the bat reaches what I'll call saturation; ie, fully charged.
Each bat should have its own BMS with an over voltage disconnect but the BMS is not meant to be a charging regulator, it is an emergency shut off. Imo it should not be 'exercised' on a regular basis just like we shouldn't be over-working circuit breakers then expect them to work as intended in an emergency.
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Nobadays
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# Posted: 15 Jul 2024 11:58pm
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Travellerw... not sure how you found that. I tried a search and got 13.2v-13.8v didn't say single stage. But if that is so... I may see if I can adjust it! Wish it wasn't so hard to remove... I did get to it easier than I thought but it's hard-wired in.
Thanks!
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Nobadays
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# Posted: 16 Jul 2024 12:02am
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ICC.... a quick question. My battery negative side goes right to the Chassis. As the Victron DC/DC charger wants both positive and negative wires, and my current isolator only has positives, you thin I can just grab a nearby grounding point onnthe Chassis and call that the negative side?
Thanks!
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gcrank1
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# Posted: 16 Jul 2024 12:22am
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Fwiw, for stuff like that I don't like chassis grounds
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ICC
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# Posted: 16 Jul 2024 12:50am - Edited by: ICC
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I believe using chassis grounds is fine as long as the cable connections are well made and unlikely to corrode. In my van the connections between the Victron and ground are not out in the weather so not likely to corrode. Plus they have a protective coating applied after connection.
Victron has both isolated and non-isolated dc-dc chargers/converters. Isolated types are specifically made for uses that do not have a ready common ground. Things like fiberglass boats.
The isolated Victron have 2 red (+) and 2 black (-) terminals. Non-isolated only a single black (-) terminal
Some differences inside.
I used an isolated unit only because I was able to get a new one in damaged packaging for less than an untouched non-isolated boxed unit.
So yes, I think a good chassis ground is fine with either Victron type. I can't think of any good technical reason to isolate, nor a reason not to isolate.
EDIT: even though I have an isolated unit, both of the negatives are connected to the same chassis ground point as if it was non-isolated
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Nobadays
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# Posted: 16 Jul 2024 01:34am
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Thanks for this explanation. All of my negatives/grounds are on the Chassis. This includes those back at the batteries and those where the converter/charger is located. Those by the batteries would be subject to moisture the other not at all. I will replace the battery isolator under the hood with the Victron DC/DC so I can grab a Chassis ground under there where it is protected.
Thanks!
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travellerw
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# Posted: 17 Jul 2024 01:23am
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Quoting: Nobadays Travellerw... not sure how you found that. I tried a search and got 13.2v-13.8v didn't say single stage. But if that is so... I may see if I can adjust it! Wish it wasn't so hard to remove... I did get to it easier than I thought but it's hard-wired in.
I've spent years honing my googlefoo ;)
Actually I found a picture on Ebay with the label. It showed the details. I then did further googling it looks like they sold 2 versions, 1 that is just a single stage and one that is 2 stage (different model number).
If you can adjust it to 13.5 then its within spec for Li.Time batteries. However I would NEVER leave it plugged in long term. I really don't trust any charger unless is talks with the BMS and turns itself off when the batts are full. Its not good to leave LiFePO4 batteries at float for long periods.
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Nobadays
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# Posted: 18 Jul 2024 01:21pm - Edited by: Nobadays
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Update on the final design. I will go with the Victron 12/12/30 charger, great equipment and easily adjusted to any chosen voltages and has a remote switch so it can be shut down if so desired. I have ordered the Progressive Dynamics PD9130LV converter/charger which has been redesign to be lifepo4 friendly. It is a 2 stage charger, 14.4v until batteries are charged then drops off to13.6v maintenance (float) charge.
I went with PD9130 as there is only a 30amp breaker protecting the charging circuit from the C/C.
I'll replace the current battery isolator with a heavy busbar to attach the wires to. I hope to mount the Victron 12/12/30 under the seat in the back. I just have to locate the charge wire coming from the current isolator.
Thanks all!
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