Difference in Charging Between Generator and Shore Power

[Wazbro]

Originally Posted by Milo1952

Just purchased 2 Lion Ut1300 lithium.
I need to upgrade my charger.
Any suggestions to which one I should get ? These are group 24 size.
Other than the charger is there anything else I NEED to do ??????
Plan on using an Renogy 200 watt suitcase or Zamp 230 w. suitcase.

You should disconnect the charge wire from the TRAILER side of the umbilical, not the tow vehicle side. From what has been said at best the tv will drain the lithium batteries while towing, at worst damage them. From the trailer side since if you break down you may forget or might not be able to get the tow driver to disconnect the charge wire on his vehicle.

[Rocinante]

This is a relevant point. Definitely worth discussing with the folks from whom you buy any drop-in lithium battery replacements for your lead acid units (e.g. Battle Born).

I had a PM asking about what charger to use if one swaps in drop-in Lithium battery replacements for the lead-acid batteries on the tongue. Several threads here discussed that topic previously. Some of them also discuss the charging issue between truck / trailer and how to manage it.

Full disclosure we did an extreme version of this upgrade, having AM Solar rip and replace our entire electrical system to go full-on lithium / solar, so when it comes to details for a less-extreme upgrade, I may sometimes be fuzzy. On the other hand, here are a couple of relevant threads that provide quite a few specifics relevant to DIY-ers. There are other threads as well, easily found by searching the forum for "lithium charging".

• https://www.airforums.com/forums/f40...bc-203510.html
• https://www.airforums.com/forums/f37...es-158116.html

[uncle_bob]

Originally Posted by Wazbro

You should disconnect the charge wire from the TRAILER side of the umbilical, not the tow vehicle side. From what has been said at best the tv will drain the lithium batteries while towing, at worst damage them. From the trailer side since if you break down you may forget or might not be able to get the tow driver to disconnect the charge wire on his vehicle.

Hi

Ok so to be fully accurate:

You need to locate the wire that runs from the tow vehicle alternator and battery back to the 7 pin connector and goes via the 7 pin connector to the DC wiring harness to the DC bus distribution block in the trailer. That wire needs to be disconnected at the DC distribution bus.

Or you can put in a DC/DC converter and solve the problem another way.

Bob

[ROBERT CROSS]

Originally Posted by Wazbro

You should disconnect the charge wire from the TRAILER side of the umbilical, not the tow vehicle side. From what has been said at best the tv will drain the lithium batteries while towing, at worst damage them. From the trailer side since if you break down you may forget or might not be able to get the tow driver to disconnect the charge wire on his vehicle.

Will damage them...How? 🤔
Maybe not sync them or top to 100%, but drain them?
7k cross country & 2 yrs use has not happened yet.




Bob
🇺🇸

[Justinfinity]

Originally Posted by uncle_bob

Hi

Ok so to be fully accurate:

You need to locate the wire that runs from the tow vehicle alternator and battery back to the 7 pin connector and goes via the 7 pin connector to the DC wiring harness to the DC bus distribution block in the trailer. That wire needs to be disconnected at the DC distribution bus.

Or you can put in a DC/DC converter and solve the problem another way.

Bob

Caution: This is very likely dependent on how the tow vehicle manages the +12V connector pin#4. For example, when the tow vehicle is running, it likely sends current "out" the 7-way connector to the trailer. However, when the tow vehicle is not running, it may open a relay on that specific #4 pin and therefore prevent back-feeding from the trailer battery bank. You have to check how your two vehicle behaves and manages that pin before summarily disconnecting or modifying it.

[Gcragg]

Why would you purposely choose a DC fridge for boondocking? They're not meant for that. Theyre meant for RV parks.
Should have bought a good three way fridge.

[Rocinante]

Originally Posted by Gcragg

Why would you purposely choose a DC fridge for boondocking? They're not meant for that. Theyre meant for RV parks.
Should have bought a good three way fridge.

I disagree with this assertion. With a good solar system and a decent set of lithium batteries, a DC fridge with a Danfoss compressor is absolutely the best choice.

[Gcragg]

Originally Posted by Rocinante

I disagree with this assertion. With a good solar system and a decent set of lithium batteries, a DC fridge with a Danfoss compressor is absolutely the best choice.

I disagree. Adding an 8 or 10amp draw when it’s not necessary is not smart Boondocking prep. A couple of 30lb propane bottles will run a fridge for months. And it’s cheap.
Also. Not everyone is Boondocking in climes where solar is that reliable. Cloudy days, snow etc can make solar very unreliable. And I’ll do all I can to avoid running a gen.
So I guess it comes down to personal preferences and getting a setup that works for you. But let’s face it. DC fridges where not designed with boondockers in mind.
And it pisses me off when manufacturers start forcing them on you by factory installing them.

[ROBERT CROSS]

Originally Posted by uncle_bob

Hi

Ok so to be fully accurate:

You need to locate the wire that runs from the tow vehicle alternator and battery back to the 7 pin connector and goes via the 7 pin connector to the DC wiring harness to the DC bus distribution block in the trailer. That wire needs to be disconnected at the DC distribution bus.

Or you can put in a DC/DC converter and solve the problem another way.

Bob

Originally Posted by Justinfinity

Caution: This is very likely dependent on how the tow vehicle manages the +12V connector pin#4. For example, when the tow vehicle is running, it likely sends current "out" the 7-way connector to the trailer. However, when the tow vehicle is not running, it may open a relay on that specific #4 pin and therefore prevent back-feeding from the trailer battery bank. You have to check how your two vehicle behaves and manages that pin before summarily disconnecting or modifying it.

You'yall...got me grey cells so hot I had to hitch up and do a run.😡

Bob
🇺🇸

Burb@1200rpm, 58mph, 8mi run....🤔 ...........post run@rest,unhitched.

[uncle_bob]

Hi

The relay in the TV is never going to be smart enough to know which way current is flowing. It simply closes a circuit. That's all a relay does. If the voltage in the trailer is higher than the voltage in the TV, current will flow from the trailer to the TV. That's just basic electricity stuff.

Lithium's like to be up above 13.6V and lithium chargers run up to 14.x V. Your vehicle electrical system in the summer *should* idle around 12.5 to 13.2 volts. If it's higher than that your battery isn't going to last very long. If it's lower than that, the battery won't get / stay fully charged.

The voltage difference is what gets the lithiums bothered when you hook straight from one system to the other. Running down the road vs parked, either way, it's an issue.


Bob

[Wazbro]

Originally Posted by ROBERT CROSS

Will damage them...How? 🤔
Maybe not sync them or top to 100%, but drain them?
7k cross country & 2 yrs use has not happened yet.




Bob
🇺🇸

Don't know, maybe near complete discharge?

Possibility of damage was mentioned in other threads so I mentioned that it could be a worst case scenario.

[ROBERT CROSS]

Our TV has no relay...so the little 'letric buggers can go anywhere they choose and wherever they went hasn't caused any concerns in 7500mi+.

Never mind...🤓


Bob
🇺🇸

[Justinfinity]

1. It doesn't matter what your charge source is or how powerful it is, the declining Charge Acceptance Rate (CAR) inherent to lead acid and AGM battery chemistries means that you will always have to dedicate more hours of charge time getting the batteries from, for example, 85% to 100%. Lithium batteries don't have this issue. They'll take all you can supply until they are at 100% and they'll do it much faster.

2. Over their life and the energy produced, Lithium batteries are less expensive than lead acid and AGM batteries. The up-front capital cost is higher but the cost per unit of energy over time is lower. Lead acid batteries are like like cheap shoes: they are a false economy.

[OTRA15]

Originally Posted by Justinfinity

. . .
. . . Lead acid batteries are like like cheap shoes: they are a false economy.

In all climates and weather conditions?

What about the fact that you can charge those old-fashioned batteries in temperatures below freezing? Not so with lithiums, right?

Our Airstream sits in the back yard all winter, where we can keep the batteries charged with careful periodic shore power. Works for us!

Do you have lithium batteries installed all winter in Connecticut, and if so, what do you do about keeping them topped up all winter?

[Justinfinity]

Originally Posted by OTRA15

In all climates and weather conditions?

What about the fact that you can charge those old-fashioned batteries in temperatures below freezing? Not so with lithiums, right?

Our Airstream sits in the back yard all winter, where we can keep the batteries charged with careful periodic shore power. Works for us!

Do you have lithium batteries installed all winter in Connecticut, and if so, what do you do about keeping them topped up all winter?

1. Lithium batteries don't need to be "topped up" because there is no sulfating risk as there is in conventional lead acid battery chemistries.

2. A lithium battery with a good BMS will manage and protect the battery according to temperature, voltage, and current.

3. A lithium battery does not need to be kept charged in freezing temperatures when in storage. However, if you wish to charge or "top up" a lithium battery in freezing temperatures, then a heat source is needed to get the battery up to a temperature at which it is safe to charge. Some installations have external heat wraps which are managed separately from the battery. Some batteries have heating pads built in and are managed by the BMS. In the latter category, when a charge source is available, the BMS will direct the external power to the heating pads and only then start charging the battery when it is safe to do so. An example of a battery that does this is LifeBlue low temperature models (this is what I have).

[OTRA15]

Thank you for those details.

Peter

[jimdelane]

Originally Posted by OTRA15

In all climates and weather conditions?

What about the fact that you can charge those old-fashioned batteries in temperatures below freezing? Not so with lithiums, right?

Our Airstream sits in the back yard all winter, where we can keep the batteries charged with careful periodic shore power. Works for us!

Do you have lithium batteries installed all winter in Connecticut, and if so, what do you do about keeping them topped up all winter?

Technology is moving faster than outdated information. RELiON has developed a new series of lithium iron phosphate batteries that can charge at temperatures down to -20°C (-4°F). They are not the only company offering low temp lithium batteries.

Also, the self discharge rate of a lead acid battery (AGM,SLA,flooded) is about 4% per week or 15% per month. So if you store for 3 months you can lose 45% capacity - basically have 5% usable Ah in the battery- based on 50% max recommended discharge. Lithium batteries self discharge at 2-3% per month. So in the same 3 month period, you lose 10% capacity and still have 70% usable amp hours in the battery - based on an 80% max discharge, although you can discharge to 100%.

Also, The energy available at low temperatures is higher in lithium batteries than in lead acid. At 0°C, for example, a lead-acid battery’s capacity is reduced by up to 50%, while a lithium iron phosphate battery suffers only a 10% loss at the same temperature.

[OTRA15]

Thanks for that info. Good to know about the low-temp lithium option.

As stated, however, we keep our OEM batteries charged during the winter with careful use of shore power, and we monitor water level etc.. For now this low-cost option works for us.

Peter

[ROBERT CROSS]

Ask the folks in Minnesota about battery heaters.
Even installed a few here in WNY.
BB has had them for sale from the start.

Bob
🇺🇸