Wiring Between Batteries

[kipkohl]

AussieGuy, great list of tools. I think I'm leaning toward a hammer crimper. They're inexpensive and I haven't read anything negative about them. Plus it's not like I'm going to be doing hundreds of crimps, so I think it would serve me well.

[Aussieguy]

Will Prowse who made the list uses a hammer one
look through that whole site a lot of good stuff there
plenty of videos too


I especially like the DIY battery builds

[kipkohl]

Yeah I've seen some of Will's vids. He's a knowledgable guy all right.

[faithie999]

interesting device!

[Boborc]

If you do not want to crimp or solder your own. They make custom length cables with your choice of connector. https://www.batterycablesusa.com/

[pgandw]

Haven't seen it mentioned in the posts, but please, please put a fuse in the parallel cables of a rating commensurate (or less to match max load) with the wire size rating.

I had a set of parallel batteries (lead acid) without fuses (dealer installed). One battery shorted one cell out. The fireworks were pretty spectacular. Hydrogen makes the prettiest blue flame you can imagine in combination with the insulation burning/melting on the parallel cables. Both battery tops blew holes before I could cut the parallel cable.

Which brings up my second safety tip - always have a tool available that can cut the largest wire size you have quickly. It's much better if the handles on the tool are insulated. It's the best way to put out electrical fires. FWIW, the batteries were on the tongue, and the whole thing was contained in the battery box.

I now use GC-2 batteries in series.

Fred W
2019 Flagstaff T21TBHW A-frame
2022 Hyundai Palisade

[Bob K4TAX]

For that very reason and others, I DO NOT connect batteries in parallel.

I recommend using a battery selection switch to allow the selection of one battery or the other battery. Thus I have the choices; #1 battery, BOTH, #2 battery, and OFF. I do use the BOTH position for charging however if there should be an issue, there is an immediate way out and OFF.

Not so with hard-wired parallel batteries.

If one insists on using the parallel connection, then the batteries must be as identical as possible: same brand, same size and rating, and same age/date code. Thus if one replaces one they should replace both.

Bob

[TitanMike]

Originally Posted by Bob K4TAX

For that very reason and others, I DO NOT connect batteries in parallel.

I recommend using a battery selection switch to allow the selection of one battery or the other battery. Thus I have the choices; #1 battery, BOTH, #2 battery, and OFF. I do use the BOTH position for charging however if there should be an issue, there is an immediate way out and OFF.

Not so with hard-wired parallel batteries.

If one insists on using the parallel connection, then the batteries must be as identical as possible: same brand, same size and rating, and same age/date code. Thus if one replaces one they should replace both.

Bob

Not an issue with GOOD LiFePo4 batteries with integral quality BMS in each.

All the "excesses" that might occur in one or the other battery will shut it off.

[Bob K4TAX]

In post #26 it appears they had a battery fire. So one must presume that FLA or AGM batteries were being wired parallel.

Of course, one can speculate that a new battery may have been connected with an old battery or visa versa. A cell shorted and a hydrogen fire occurred. These by the way are darn impressive.

Bob

[kipkohl]

I'm planning on fusing at the battery if there isn't a fuse already in place.

[RVasylum]

Originally Posted by TitanMike

As it is right now the largest draw on your 12v system will be the inverter. Current draw, allowing for inefficiency will be more like >90 amps. This will be in addition to the usual 12v load for lites, refer, t-stat, etc. I'd use 100 amps for determining wire size as a minimum.

Using an average total wire run from load to batteries of 20 ft, and using a chassis ground, a #1 awg wire would be minimum. #8 wire doesn't even make the chart with a 1000w inverter but no surprise a dealer would think so.

If you see a larger inverter in your future go as large as you'd need in the future. More $$ for the larger wire initially but cheaper in the end as you'll only be buying wire once.

Correct me if I’m wrong but with Lithium batteries and their high .5 to 1 C charge rates isn’t it correct to also take the charge rates into account when determining wire size. If you do not use a high load item like a inverter but you use a 50 amp dc/dc charger the wire size needs to be able to handle the higher Lithium charge rate also.

[TitanMike]

Originally Posted by RVasylum

Correct me if I’m wrong but with Lithium batteries and their high .5 to 1 C charge rates isn’t it correct to also take the charge rates into account when determining wire size. If you do not use a high load item like a inverter but you use a 50 amp dc/dc charger the wire size needs to be able to handle the higher Lithium charge rate also.

When determining the wire size for use with any battery it's important to use the highest expected current regardless if it's charge or discharge current. Also a good idea to include an extra margin to minimize voltage drop.

You're right about Lithium batteries using the max output of a charger.

[kipkohl]

I'm back with another question. As I stated a few posts ago, the 2 Lion UT1300's were installed and seemed to be working fine.The Go Power 30a charge controller showed 14.6v charge on the batteries, and the lights were working fine while my wife and I took some measurements inside. Trailer is still at the dealer waiting for the hitch and some other work. Anyway, when we left I turned the battery switch off and the charge controller started flashing. I told the the service guy and he said that was normal. Well, yesterday he called back and said that the flashing was an over charge error message. So they took the lfp's out and re-installed their lead acid batteries and everything seemed normal.
Anyone have any ideas what would cause the over charge message? At the time solar was the only charge source, there was no shore power hookup, plus it was only when I turned the battery switch off that the flashing began. There's 2 190w solar panels and the 2 105ah batteries.
Thanks in advance for any info anyone can offer.

Kip

[CHICKDOE]

this is only a guess. but if there is no shore power and you have disconnected all the loads from the batteries the only thing attached to the batteries are the panels and the solar charge controller. what does the charge controller manual say that the flashing light represents?

my guess would be that the charge controller is still configured for lead acid batteries and the lithium are presenting different characteristics that the charge controller is assuming is an overcharged lead acid battery. you may need to change the charge controller configuration to specify it is charging lithium batteries.

again only a guess, but with everything else removed it is between the charge controller and the batteries. charge controller seems ok when connected to lead acid but not ok when connected to lithium. there was no mention of changing the charge controller configuration between the two battery types.

[kipkohl]

Go Power says the flashing is an over charge error. The service guy says the controller was switched to LiFePO4 setting, but I wonder. He's a nice guy who seems to know a lot about general RV stuff, but admits they don't deal with lithium batteries and he is not familiar with them.
So, we'll pick up the trailer on Monday and I'll look into it when we get home. Just thought I'd pick people's brains in the meantime. Thanks for your input.

[TitanMike]

Originally Posted by kipkohl

Go Power says the flashing is an over charge error. The service guy says the controller was switched to LiFePO4 setting, but I wonder. He's a nice guy who seems to know a lot about general RV stuff, but admits they don't deal with lithium batteries and he is not familiar with them.

So, we'll pick up the trailer on Monday and I'll look into it when we get home. Just thought I'd pick people's brains in the meantime. Thanks for your input.

When you turn the batteries off there's no place for output of solar controller to go. Voltage will climb and this is most likely causing the flashing light.

Unless output of solar panels is switched off, controller should always remain connected to batteries.

If I read you original post correctly all was OK before batteries switched off.

Either connect the output of the solar controller to the " always hot-" side of battery switch or add a switch that will disconnect solar panels before turning battery switch off.

[Tombsy]

Originally Posted by TitanMike

When you turn the batteries off there's no place for output of solar controller to go. Voltage will climb and this is most likely causing the flashing light.

Unless output of solar panels is switched off, controller should always remain connected to batteries.

If I read you original post correctly all was OK before batteries switched off.

Either connect the output of the solar controller to the " always hot-" side of battery switch or add a switch that will disconnect solar panels before turning battery switch off.

The same thing happened with my Go Power controller, I had them wire it to the “always hot” side of the controller as mentioned by Titanmike.

[kipkohl]

Originally Posted by TitanMike

When you turn the batteries off there's no place for output of solar controller to go. Voltage will climb and this is most likely causing the flashing light.

Unless output of solar panels is switched off, controller should always remain connected to batteries.

If I read you original post correctly all was OK before batteries switched off.

Either connect the output of the solar controller to the " always hot-" side of battery switch or add a switch that will disconnect solar panels before turning battery switch off.

Correct, only with the batteries off. Tech states with the LA batteries hooked up, no error message. I'm not positive, but I think the solar bypasses the battery switch on Geo Pros/E Pros

I'm leaning toward the idea that the charge controller may not have been in Li mode.

[TitanMike]

Originally Posted by kipkohl

Correct, only with the batteries off. Tech states with the LA batteries hooked up, no error message. I'm not positive, but I think the solar bypasses the battery switch on Geo Pros/E Pros



I'm leaning toward the idea that the charge controller may not have been in Li mode.

Not being in Lithium mode would merely reduce the peak charging voltage and it's duration. No different than using a standard converter with Lithium batteries. Max charge won't be achieved but no high voltage errors.

Your issue sounds more like the controller is NOT connected directly to the batteries even though the Tech says so.

The connection is often made at the battery switch and the error is merely a matter of someone picking the wrong terminal. If the connection was made at the battery you wouldn't be having this issue.

[kipkohl]

TitanMike, what you're saying makes sense, but why no issue with the LA batteries? I'll be glad when we can get it home, and I can go through it myself.