batteries in lmtv?

[BuiltMFG]

Where do you normally get those?

Amazon has them. Low quantities are about a $1 each, higher quantities are about .50 each

 

[BuiltMFG]

Aernan, here is the additional specs n the batteries,
Eveready Group 31 Commercial | Cranking amps 1185 | Cold Cranking 950 | Reserve 195
They were about $80 each after core charge


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[Aernan]

BTW if you do end up buying batteries from NAPA when you order the acid it comes in the large 6L quantities. You need one box per battery. The local guys had never dealt with a dry cell before. The acid goes into the battery and you charge it completely. Then if the levels are not high enough you add distilled water. You don't need a specific gravity tester.

 

[Ohiobenz]

Has anyone gotten pricing on the LiFePo batteries? They are 1/2 the weight...

 

[Awesomeness]

Has anyone gotten pricing on the LiFePo batteries? They are 1/2 the weight...

My guess is they are probably a few times the cost of a regular battery. Of all the benefits of them, I'm curious why the weight is what you mention?

 

[Ohiobenz]

The 6T equivalent is only 45lbs...

 

[Aernan]

No one got the pricing on the LiFePo4 batteries. I did send a RFQ but never got a response. The mass does not make any sense. The 6T AGM is like 86 lbs. LiFePo4 is like 10x energy density on Lead Acid. http://www.batteryspace.com/batteryknowledge.aspx by mass it should be 1/5. That puts it at 17.8 lbs but who knows how much the protection circuit and casing weigh.

 

[Ohiobenz]

It appears the case is aluminum.

 

[Aernan]

I am going to stick with the simple Lead Acid 6T batteries in my vehicle. I plan on converting the bed to an RV where I will put a LiFePo4 as a house battery. I will use the "starting batteries" to start the vehicle and run loads in the cab like GPS and Radios. I will most likely add a 1-2kw inverter to those starting batteries to run AC loads until I get my camper on the back built.

Chances are good that the Lithium batteries available as a drop in replacement are very expensive. If you do use them to 100% drain you still need to start the truck to get them charged again. I guess you might rig up some kind of system with 2 lead batteries for starting and 4 lithium for loads so you can store all batteries in that one spot.

Another consideration is Lithium batteries perform poorly or not at all in cold weather. I would like to drive my truck to snowy environments and still be able to start it. You could get around that design limitation by using an electric heater to keep the batteries in the usable temp range.

 

[DiverDarrell]

Do you always have to keep the batteries warm or just when charging and using? I will more than likely run the truck on two 8D batteries, and some kind of agm deep cycle for the house batteries in 24v for inverter efficiency, and allow to cross connect to start the truck in an emergency. 6TL’s are just not worth the cost in my opinion. Keep up the battery talks, good info

 

[Aernan]

I had a ballistic performance Lithium motorcycle battery. I never ended up installing it because some other owners had put them in bikes and had a hard time getting the bike started in 32 degree F or lower temp. I believe you can store them safely at lower temps but you won't be able to use them as a starter battery. Another interesting thing is using the battery creates internal resistance which warms the battery. So if at first the vehicle does not crank over fully just keep doing it and eventually the battery will get to high enough temp to supply enough current to start the motor. The real problem is this is the same symptom as a dead/low battery so it's disconcerting.

As far as AGM deep cycle batteries as a house battery. I strongly recommend against it. Lithium batteries can be discharged 1000 times. After that you lose 1% of total capacity each full discharge cycle (or cummulative). A lead acid on the other hand you get 200 charge cycles. To make a lead acid battery last any time you de-rate it to 50% usage and you may also de-rate it further for a longer lifespan. So when doing your math about capacity you need to at a minimum double it. Another thing to consider is that they are big and heavy. Lead -> LiFePo4 10x -> LiPo 12x energy density but then if you add the de-rating you get 20x and 24x lighter. There are some other drawbacks to Lead. It offgasses hydrogen which is flamible and you are dealing with electricity so sparks are common when connecting/disconnecting and can be present in relays. Vented storage is required for certain and electrolyte top up may be required. The only big advantage to Lead is no complex charge/discharge circuits and it's cheap.

Your last point of using 24V to interconnect for starting (emergency). It would be nice to have some emergency starting options but in the near term I plan on keeping my starting batteries healthy and avoiding doing anything to draw on them when the engine is not running.

From my research I plan on doing something novel/unique. I am sizing my battery pack to be able to run an Air Conditioner. Typically the AC is the biggest draw in an RV. In fact it draws so much power the you either must be on mains (utility power in an RV Park 15-20 amp circuit) or be running a generator (very noisy). After some digging I found out that mini split inverter based AC are literally 3x the efficiency of the AC units typically used in RV units. Another place to save power is to avoid the DC -> AC -> DC conversion. Internally the mini split uses -48V DC to drive the motor. I plan on opening my unit (void the warranty) and powering it directly. To make this work I will make my pack 48 VDC.

This does cause all sorts of other problems because most DC electronics are designed to work on 12, 24VDC. DC -> DC step down conversion is very efficient so I will run a step down converter to make a common 12V and 24V power circuits to run all my electronics when possible as well as running a small 1000-2000 Watt inverter. Looking at inverters you can get AC synchronized models where you can add 1k at a time up to 4k I believe so you don't get massive switching losses by running a huge inverter for small loads.

For emergency starting I will use my 48-24 circuit to charge the starting batteries high enough that I can start.

 

[firefinder]

Great discussion here!

I'm not a battery engineer, but I have been trying to learn about some of the lithium based technologies. I ran across some YouTube videos and found a website that sells Tesla components. The Tesla batteries have a liquid thermal exchanger built in to allow for heating and cooling. The thermal exchanger prevents the batteries from getting to cold in the winter and obviously too hot from use. Might be an interesting project to develop a hydronic heater circuit to warm the batteries in winter. The weight to amp hour characteristics are phenomenal!! But the cost is up there too. Check out some of the electric power plants too.

https://hsrmotors.com/hsr/products

 

[Aernan]

That's an awesome find. I didn't realize you could buy those independent of the vehicles. They are based on the 18650 lipo battery pack. . The great thing about the tesla battery packs is the packaging and cooling. Now that I know they are available I'll look to see if I can integrate them into my design.

Tesla is about to start making an new format for batteries the 2170 which will be a huge improvement
https://insideevs.com/tesla-2170-battery-cells-greater-power-comparable-cost/

I'm not a battery engineer either but luckily I work with some excellent electrical engineers who can help me make sense of the complexities of designing an electrical system for the camper portion.

https://hsrmotors.com/hsr/products/battery_module_100
285 Ah for $2000 = $7.017 per amp hour

http://www.batteryspace.com/lipo-battery-pack-tattu-22-2v-22ah-488-4wh-25c-6s1p.aspx
22 Ah for $450 = $20.45 per amp hour

http://www.batteryspace.com/lifepo4...96v-choose-from-40ah-60ah-or-100ah-w-can.aspx
220 Ah for $13,650 = $68 per amp hour

https://parts.cat.com/en/catcorp/8T-9731
8T Lead Acid
156 Ah for $186 = $1.19 per amp hour

The tesla battery is a great value.

 

[Ohiobenz]

Since my M1079 is being delivered tomorrow with bad batteries, and I need to drive it off the trailer, I just dumped $800 into four 6TMF DEKA batteries.
The Tesla info will come in handy when I work on the RV part...

 

[VVFD]

We got ours from NAPA also... for about the same price. They are the same size as the MIL batteries and fit snug. Did not have to make any spacers. Battery posts are in the same location, so all the cables fit perfectly.

 

[Awesomeness]

Everything has pro's and con's. While the LiIon and LiPo batteries are much more energy dense (e.g. smaller and weigh less for same charge), they have the heating and cooling issues that have been mentioned, cost a lot more, can be fire risks, etc. On trucks like these, it seems space and weight are not really issues (within reason), so what's really the advantage? Just cool factor?

 

[deshet]

I am in a different situation. I am going to fly in a retrieve a truck with a 1000 mile trip ahead of me.
The truck will jump start but I want to replace the batteries with group 31s for the long trip. Is this a straight forward to replace 4 original military batteries with 4 group 31s?
Thanks

 

[BuiltMFG]

I am in a different situation. I am going to fly in a retrieve a truck with a 1000 mile trip ahead of me.
The truck will jump start but I want to replace the batteries with group 31s for the long trip. Is this a straight forward to replace 4 original military batteries with 4 group 31s?
Thanks

Well, the tray will not allow for it. And you have to mess with the cables to get them to reach. Visit my website to see what it took for me to make it work.


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[deshet]

I don't need a premenant install.
I would be fine with the top of the box removed and straps holding the batteries down.
If I am willing to do this can I install groups 31 pretty easily?

Thanks

 

[BuiltMFG]

I don't need a premenant install.
I would be fine with the top of the box removed and straps holding the batteries down.
If I am willing to do this can I install groups 31 pretty easily?

Thanks

Yeah probably, if the cables don’t reach you can probably let get away with installing 2 batteries and be good for the trip.


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