What would you do?

[T1 Terry]

My passion and now my half on a business is designing and assisting the install of lithium battery and associated charging systems. I have been involved in some very heavy power user set ups, all have 3 charging methods, DC to DC for alternator charging, mains charger for both mains and generator charging if needed and solar. We make an interface so any charging method already in the use that still works well can be used for lithium batteries, no point in throwing away something that still works eh In most installs the main source of charging is predominantly solar and secondary is DC to DC charging.
I'll write a separate article on cable sizing and link it here so it makes it easier for all to reference if they wish... or ignore if they wish

There is no such thing as one size fits all, the balance is all to do with travel modes, and power use. We don't build many systems for the roughing camper who believes a tent and Tilley lamp are luxuries
Travel mode ranges from:
Drive between caravan parks and just need the fridge, coffee machine, air con and what ever powered for the lunch breaks
Drive each day to a new free camp site
Max 3 day free camp and then to a caravan park or long drive to the next 3 day free camp
Long free camp stays and a toad/tug to do the trip to town and site seeing ventures
each is different in the way the balance is set up so as you can there can really be no such thing as a one size standard system.
One method not often thought about is using the toad/tug as the transport method for stored energy as well as water, food and waste transfer. Part of the over all battery pack in in the toad/tug and charged via DC to DC and even mains charging from town as many recharging spots are appearing to support the roll out of electric vehicles. 3 phase power outlets have the potential to power 3 large chargers, lithium batteries will accept very fast charge rates so 3 x 50 amp chargers will fill a 400Ah battery pack drained to 20% SOC in 2 hrs, cart that back to the home base and top up the house battery via the DC to DC charger to make up for the solar shortfall in crap weather, it then doubles as a storage bank when the solar is exceptional.

So, which type of free camper are you Grizz and what sort of system/capacity were you looking at?

T1 Terry

[grizzzman]

Hi ya Terry
So, which type of free camper are you Grizz and what sort of system/capacity were you looking at?

Perhaps my goal with this trailer will help. In 7 years (or less) I will retire At that time longer trips (weeks) would be likely. Using the tug would not be a problem but it would need to be removable. I would like to use the microwave now and again and perhaps a coffee pot as far as high amps use goes.
I would say that when I retire my needs (well wants) will be higher. I'm thinking a 300 AH battery pac would get the job done. I'm thinking solar and alt (DC to DC) would be in order with a fall back mains charger. What do you think?

Thanks Terry

[T1 Terry]

Hi ya Terry
So, which type of free camper are you Grizz and what sort of system/capacity were you looking at?

Perhaps my goal with this trailer will help. In 7 years (or less) I will retire At that time longer trips (weeks) would be likely. Using the tug would not be a problem but it would need to be removable. I would like to use the microwave now and again and perhaps a coffee pot as far as high amps use goes.
I would say that when I retire my needs (well wants) will be higher. I'm thinking a 300 AH battery pac would get the job done. I'm thinking solar and alt (DC to DC) would be in order with a fall back mains charger. What do you think?

Thanks Terry

A sensible approach, if the tug will be used regularly but the trailer only moved once every so often then the majority of the charging system and battery capacity should be in the tug, transfer it to the trailer via the DC to DC charger when needed, just like pumping water. Set the solar up on the trailer roof but link the tug and trailer together when you are there so the solar is also stored in the tug battery bank once the trailer battery is full.
a 100Ah lithium battery will run a microwave or a coffee machine, but you would only be likely to use those while you are there with the tug, then the 200Ah in the tug plus the 100Ah in the trailer gives you 300Ah to run the higher draw appliances, yet the 100Ah to keep the other stuff powered while you are away.

T1 Terry

[grizzzman]

Hi ya Terry
So, which type of free camper are you Grizz and what sort of system/capacity were you looking at?

Perhaps my goal with this trailer will help. In 7 years (or less) I will retire At that time longer trips (weeks) would be likely. Using the tug would not be a problem but it would need to be removable. I would like to use the microwave now and again and perhaps a coffee pot as far as high amps use goes.
I would say that when I retire my needs (well wants) will be higher. I'm thinking a 300 AH battery pac would get the job done. I'm thinking solar and alt (DC to DC) would be in order with a fall back mains charger. What do you think?

Thanks Terry

A sensible approach, if the tug will be used regularly but the trailer only moved once every so often then the majority of the charging system and battery capacity should be in the tug, transfer it to the trailer via the DC to DC charger when needed, just like pumping water. Set the solar up on the trailer roof but link the tug and trailer together when you are there so the solar is also stored in the tug battery bank once the trailer battery is full.
a 100Ah lithium battery will run a microwave or a coffee machine, but you would only be likely to use those while you are there with the tug, then the 200Ah in the tug plus the 100Ah in the trailer gives you 300Ah to run the higher draw appliances, yet the 100Ah to keep the other stuff powered while you are away.

T1 Terry

I have a few question's if you don't mind Terry. When the battery is in storage (between trips) during the summer could be subject to 48 C temps when parked in the sun. This would happen during the week and to a lesser degree the trailer would do the same. In the winter here can get as cold as -23 C (thank goodness not often) I think to solve that would be to pull the packs in the winter but to pull and install packs every week during the summer would...... Well........suck can the packs handle the temps? I like the idea of a pack in the tug but wouldn't it require two bms ? One for the tug and one for the trailer?

Thanks Terry

[grizzzman]

Hi ya native pepper
Is this the device you speak of? https://www.aliexpress.com/store/produc ... 27736.html If so it looks like you would need to disconnect it during storage?

Thanks

[native pepper]

Hi ya native pepper
Is this the device you speak of? https://www.aliexpress.com/store/produc ... 27736.html If so it looks like you would need to disconnect it during storage?

Thanks

That looks like the one, have never disconnected mine, they seem to shut down when the cells are equalised. Then again I use my packs daily, the bus is the only one that would sit for any time and I disconnect the lifepo4 pack from the panels and the gel pack takes the panel energy, as lead acid likes to be topped up constantly because of the loses, whilst lifepo4 doesn't. You could always disconnect the equalisers or use alligator clips. I have lifepo4 cells that have sat for close to 5 years and they still sit at 3.4v, have them as spares but never had to use them.

When storing if your going to us lifepo4, you can store them at the temperatures you quote I believe, the problems arise when they are in use with high and very low temps and you need big current draws. In tests I've seen the best temps for lifepo4 are between 18-24degC, but doubt anyone can keep them around those marks without aids. I know of installations in central Aus that use peltiers to keep their packs in check and they have temps from below zero to close to 50degC. A well insulated pack or container would help in really cold climates.

Where I live we get below zero during winter, but it's only a degree or two and rarely stays that way during the day. Remember if you're going the lifepo4 way, you can put them anywhere, even use them as foot stools in your rig, they are so safe.

[bob r]

I have a 200 amp lith set up in the van runs the fridge TV lights computer charging thru a 1000 Watt inverter, in the ute I have a 400 amp lith set up with a 3000 Watt inverter when using the induction cooktops or the microwave the small fan heater or the skillet I run a lead from the ute to the van works great.

Bob

[T1 Terry]

Hi ya native pepper
Is this the device you speak of? https://www.aliexpress.com/store/produc ... 27736.html If so it looks like you would need to disconnect it during storage?

Thanks

I am testing these at the moment, can't leave them connected to a battery that isn't being charged regularly as they will flatten the battery. We are in the process of designing a unit to turn these balances on only when required, that way they don't hide a problem that would be easy to see without the balancers. Better to sort the problem before it becomes so big the balancer can't contain it, by that stage the problem may well be serious where early intervention would have solved the issue with no damage done.

T1 Terry

[T1 Terry]

I have a few question's if you don't mind Terry. When the battery is in storage (between trips) during the summer could be subject to 48 C temps when parked in the sun. This would happen during the week and to a lesser degree the trailer would do the same. In the winter here can get as cold as -23 C (thank goodness not often) I think to solve that would be to pull the packs in the winter but to pull and install packs every week during the summer would...... Well........suck can the packs handle the temps? I like the idea of a pack in the tug but wouldn't it require two bms ? One for the tug and one for the trailer?

Thanks Terry

Yes, a BMS for each battery, The battery would need to be inside the trailer if -23*C was experienced regularly while in full use, I sure wouldn't want to be there The 48*C is within their capabilities. Winston Batteries say their cells can operate between -48*C and 85*C both charging and discharging, but the loads would need to be gentle I would think, maybe 0.1CA or 10 amps per 100Ah capacity either way to avoid localised cell heating. The heat produced could equalise throughout the cell at a low load/charge rate and once warmed there would be no problem regarding load. A temp sensor between the cells would give a good indication of the heat spread throughout the cell, just on the terminal bolt will indicate very little due to the way the cells are built, nothing like the way lead acid batteries are constructed.

T1 Terry

[grizzzman]

I have a 200 amp lith set up in the van runs the fridge TV lights computer charging thru a 1000 Watt inverter, in the ute I have a 400 amp lith set up with a 3000 Watt inverter when using the induction cooktops or the microwave the small fan heater or the skillet I run a lead from the ute to the van works great.

Bob

Hiya Bob
Looks like a well working split battery system.for sure. The more I think of it, the more sence a split system makes. Thanks for sharing.