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Old 07-03-2018, 07:57 PM   #1
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THOR #12189
Wet Cell to Lithium - Straight Swap Charging Question

Sorry for the repost. I tried to include a link to my Progressive Dynamics reference and it canned my post. I tried to find it and could not. Black holes are real.

I'd like to swap the two wet cell house batteries for two lithium. Does anyone know if the existing charging equipment: converter/inverter, generator, battery management system and alternator will properly charge the lithium batteries?

Has anyone personally done this and can verify the following:

Question: ďMy Present RV has a 45-Amp Converter/Charger. Can I Install a Larger 60-Amp or 80-Amp Unit to Further Reduce My Recharge Time?Ē

Answer: ďNo, your RV wiring system is designed to safely handle 45-Amps increasing it to a 60 or 80-Amp charger could cause a thermal event! When updating to a Lithium Battery System, stick with the same size Converter/Charger as presently installed in your RV! Again with the faster charge rate that Lithium Batteries can accept even a 45-Amp Lithium Charger can recharge a 100-AH Battery, (100-AH divided by a 45-Amp charge rate) that would equal about 2.2 hours plus the extra time required at the end of the charge due to a lower charge rate, would equal an estimated recharge time of approximately 3 Hrs.Ē (re: Progressive Dynamics FAQ)
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Old 07-03-2018, 08:39 PM   #2
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The answer PD gives assumes that the converter will produce 45 amps to the batteries. But with two 6 volt batteries in series all the amps the converter might produce would go to both batteries; otoh if you have two 12 batteries in parallel the current would be about half to each.


You need to carefully study what the battery manufacturers requirements are for charging and then size your charger and wiring accordingly.
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Old 07-04-2018, 12:26 PM   #3
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Originally Posted by scrubjaysnest View Post
The answer PD gives assumes that the converter will produce 45 amps to the batteries. But with two 6 volt batteries in series all the amps the converter might produce would go to both batteries; otoh if you have two 12 batteries in parallel the current would be about half to each.


You need to carefully study what the battery manufacturers requirements are for charging and then size your charger and wiring accordingly.
Thanks Scrub. I (careful here) 'assume' you mean the wiring from the charger to the batteries and I'm not changing wiring in the walls, ceiling or floors??

Have a safe and happy 4th of July.
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Old 07-04-2018, 03:54 PM   #4
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Not sure I'd even want lithium batteries in my coach. After the problems Boeing had with it's Dream Liner and "thermal event" battery fires, I'll stick with wet cells.
If you go to lithium I hope all works well for you.
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Old 07-04-2018, 04:48 PM   #5
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Originally Posted by RvEd View Post
Thanks Scrub. I (careful here) 'assume' you mean the wiring from the charger to the batteries and I'm not changing wiring in the walls, ceiling or floors??

Have a safe and happy 4th of July.
That's correct the charger wiring to the batteries. Not the 120 vac.


And to piggy back on Mustang46555 said lithium batteries for RV's aren't there just yet although they are getting close.


I've personally had lithium batteries for hand held radios over heat in the charger that is made for them.
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Old 07-04-2018, 05:02 PM   #6
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The problem with Li-Ion batteries overheating is that an internal short develops within one of the cells and causes a thermal runaway condition that will typically destroy any nearby cells (or the whole battery).

Typically a short will develop if the battery is over discharged (see here for a long explanation).

I've had relatively large Li-Ion batteries in my past 3 vehicles now without any issue (23kWh, 8kWh, and now 60kWh)--two of which had/have thermal management controllers to keep temps in line. In all cases the batteries are prevented from discharging too much.
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Old 07-04-2018, 05:34 PM   #7
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Quote:
Originally Posted by scrubjaysnest View Post
That's correct the charger wiring to the batteries. Not the 120 vac.


And to piggy back on Mustang46555 said lithium batteries for RV's aren't there just yet although they are getting close.


I've personally had lithium batteries for hand held radios over heat in the charger that is made for them.

Thanks Scrub. That helps. I know what you're talking about. I use LiPos in RC planes. That doesn't make me an expert, just oriented and they're subject to that too if you don't handle them the way you're supposed to.


Quote:
Originally Posted by JamieGeek View Post
The problem with Li-Ion batteries overheating is that an internal short develops within one of the cells and causes a thermal runaway condition that will typically destroy any nearby cells (or the whole battery).

Typically a short will develop if the battery is over discharged (see here for a long explanation).

I've had relatively large Li-Ion batteries in my past 3 vehicles now without any issue (23kWh, 8kWh, and now 60kWh)--two of which had/have thermal management controllers to keep temps in line. In all cases the batteries are prevented from discharging too much.
Thanks Jamie. Did you have the luxury of trying out different brands and would you recommend one over the other? I'll have limited space in the existing hold down trays so I may wind up just finding something that fits. Still, it's good to have a recommendation going in.

Happy 4th everyone.
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Old 07-04-2018, 06:33 PM   #8
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Originally Posted by scrubjaysnest View Post
The answer PD gives assumes that the converter will produce 45 amps to the batteries. But with two 6 volt batteries in series all the amps the converter might produce would go to both batteries; otoh if you have two 12 batteries in parallel the current would be about half to each.

.....cut.....

In practice, as long as youíre comparing apples to apples regarding battery-bank size and capacity, itís not an issue to worry about because it offsets itself due to different battery Amp-hour ratings.

Itís probably easier to show this as an example:

Assume the two batteries have 200 Amp-hour combined capacity at the 12-Volts the system operates.

With 6-Volt batteries, youíd have two in series rated at 200 Amp-hours each.

With 12-Volt batteries, youíd have two in parallel rated at 100 Amp-hours each.

If the converter puts out 45 Amps, youíre correct that each 6-Volt battery sees the full 45 Amps; while 12-Volt batteries see 22.5 Amps each.

However, 45 Amps for a 200 Amp-hour battery is essentially the same charging rate as 22.5 Amps for a 100 Amp-hour battery.


I just wanted to point out that using 6- versus 12-Volt batteries isnít going to make a whole lot of difference and will therefore not make a significant difference in how fast they recharge. Again, assuming total battery bank capacity and chemistry are the same.
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Old 07-04-2018, 07:03 PM   #9
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RvEd, I canít answer your question directly, but will give you a couple of points to think about.

First, Iíll admit to being biased because I like idea of lithium batteries a lot, but would not personally spend the money it takes to upgrade to lithium if I was left with such slow charging rate. To some degree it defeats the purpose. If I was going to upgrade, Iíd upgrade all the way including wiring as needed. If not practical to rewire, Iíd enjoy system as is.

Many who upgrade to lithium batteries do it so they can power high-capacity inverters which require large low voltage (12-V) conductors. If youíre thinking of going this route, you can buy an Inverter/Charger with a high capacity converter built in, and they will also have the transfer switch built in. People who do this often install Inverter/Charger near batteries to keep cables short, and then turn off the motorhomeís converter by opening its breaker at panel. That way you can keep it as a back-up in case Inverter/Charger goes out.

One last thought to consider. Even the 80 Amp converter uses up to 1,300 watts. If you upgrade to that level, or even higher, youíll be using as much power as an air conditioner, or maybe more. If you have a 30-Amp motorhome, you may want to do an electrical energy estimate to make certain you can run essentials at same time. With a 50-Amp motorhome, supplying enough power to converter should not be a problem.
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Old 07-04-2018, 09:51 PM   #10
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...but would not personally spend the money it takes to upgrade to lithium if I was left with such slow charging rate. To some degree it defeats the purpose. If I was going to upgrade, Iíd upgrade all the way including wiring as needed. If not practical to rewire, Iíd enjoy system as is.

Many who upgrade to lithium batteries do it so they can power high-capacity inverters which require large low voltage (12-V) conductors. If youíre thinking of going this route, you can buy an Inverter/Charger with a high capacity converter built in, and they will also have the transfer switch built in. People who do this often install Inverter/Charger near batteries to keep cables short, and then turn off the motorhomeís converter by opening its breaker at panel. That way you can keep it as a back-up in case Inverter/Charger goes out.

One last thought to consider. Even the 80 Amp converter uses up to 1,300 watts. If you upgrade to that level, or even higher, youíll be using as much power as an air conditioner, or maybe more. If you have a 30-Amp motorhome, you may want to do an electrical energy estimate to make certain you can run essentials at same time. With a 50-Amp motorhome, supplying enough power to converter should not be a problem


Thanks much for all the info Chance. You brought up some good points I hadnít seen before.

I would definitely upgrade between the converter and batteries and I have seen the cable length considerations. I was mainly concerned with the wiring behind the walls and ceiling running to lights, outlets, etc, though I donít know why.


I'd planned on starting with the batteries to gain the advantage those alone might provide (discharge and cycles) and work my way back to solar. Next item would be a pure sine inverter/converter combo @ 1300 or 1500 watts. I think 2000w is a bit overkill in a 30 amp coach. I donít have the battery storage capacity to produce that output. Nor pulling that much through the system in a 30amp coach? If I ran the air, Iíd be plugged in or running the generator.

I was worried about tearing into walls and/or ceilings. It's a 2017 so I don't want to start hacking it up just yet. From what you say, it sounds like if I try to run too much stuff and draw too much juice, she'll run hot and throw breakers, leading to more serious damage.

I'm glad you chimed in. Thanks again and Happy 4th.
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Old 07-04-2018, 10:31 PM   #11
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Quote:
Originally Posted by RvEd View Post
Thanks Jamie. Did you have the luxury of trying out different brands and would you recommend one over the other? I'll have limited space in the existing hold down trays so I may wind up just finding something that fits. Still, it's good to have a recommendation going in.

Happy 4th everyone.
Well, not really: The cars I had Li-Ion batteries in:
  • Focus Electric 23kWh
  • C-Max Energi 7kWh
  • Chevy Bolt 60kWh
All batteries were included.
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Old 11-16-2018, 04:00 AM   #12
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RVEd I am curious on your choices and results, as I find myself thinking about the same series of upgrades over time (Inverter, bigger battery storage, Solar...etc). Here is my thought process.

I just purchased a used 2018 Thor FW 30D which doesn't have a factory inverter. I'd like to run the TV's and some 110 stuff without having to kick on the generator, so I would probably first like to drop in an Inverter. Now Pure Sine wave generators have really come down in price, so perhaps I can spend just $100-200 more for a bigger 3000W-4000W inverter. I currently think I wont likely use that much power regularly... but if I'm doing this work... why not drop in the bigger and not have to worry about how much I'm pulling at any one time?

Of Course, I will probably need to rewire Battery <-> Inverter for the current that will pull to feed that potential AC Draw... not a big deal, I can probably locate the Inverter near the battery bank for short DC Heavy Gage wire and run a longer AC feed to the Breaker panel (AC requires lower gage for more current).

Im sure the next step, I will look to upgrade my battery bank (currently 2 Lead acid ??AH), maybe not right now and I would have to see how rapidly the batteries drain with the new Inverter and normal use. (Also I'm not sure how the previous owners cared or cautioned from overdraining the batteries - so damage is not known). When that time comes I would probably prefer to splurge and drop in 2 lithiums instead (for all the benefits they carry). If I do that I probably have to change the Converter since my factory one probably doesn't match the charge staging for the Lithium vs Lead Acid profiles (?). Maybe the new Inverter, if I choose carefully can support the charge profile for the lithiums(?). I wonder does my chassis alternator charging have to change anything for lithium?

If the Lithium and Inverter combinations work out great, I can see myself being able to do MORE Boondocking, which would lead to my next big upgrade.. a solar package!!! My Coach is "Solar Ready" with a connection port on the roof, but not sure how this would tie into my planned upgrades and mods.

My goal is to do this over time, as we decide the right pieces and the right components, of course trying to not spend a mint... but spending wisely for good components that would be used throughout the journey (Not wanting to discard anything). This is along winded way of wondering your decisions and how you made out?
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