Big current needs in bed of Gladiator. Home run, or 2nd battery and gauge concerns......

[luthj]

This was designed with lead/acid 6V duracell battery bank, right? So if there is 220AH total, how much of that capacity is usable? I thought i read not to go past 50% use from a lead acid, so around 110AH usable?

The 50% hard line is mostly a myth. With true deep cycle batteries you can discharge down to 80% without a major impact on *total lifetime* AHs delivered.

Lead Acid 50% DOD Limit; Rule or Myth

Greetings. I have a fair amount of experience with lead acid deep cycle batteries in vehicle and PV systems (fork lifts, golf carts, small EVs, etc). I have seen/heard the following truism for as long as I can remember. "Don't discharge your lead acid batteries below 50% ever" I believe...

expeditionportal.com

For easy math assume a battery delivers 10,000 AH over its life. If you discharge a 100AH battery down to 50% you will get about 10,000/50=200 cycles. If you discharge to 80%, you will get 10,000/80=125 cycles. Te reality is not quite linear, so it would be something like 220 and 110 cycles, but the total AH delivered would be close. The biggest issue is being able to recovery the discharged AHs. Lead acid does not like to sit partially charged. At least once every 2-3 cycles (or 1-2x a week) the battery must be charged to a true 100%, this takes 8 or more hours at the correct voltage. Ideally this would happen after every deep discharge, but reality gets in the way.

Those golf cart batteries can supply 150A at a reasonable voltage drop for the top 50%. If you drop below 50% SOC, and try to pull 150A, the voltage may drop too low for the inverter.

The first step in an electrical system is to make a rough budget for AHs or watt-hours. This means a tally of all the consumers, their real world current or watt consumption, and then how often they are used. Do the same for charging if available. From there you can start refining whats possible.

 

[john61ct]

Yes there is no sharp boundary at 50%, it's a guideline, greyscale curve of **average** DoD, going down to 60-70% frequently will drastically cut cycle lifespan compared to staying above 50%.

Once in a while hitting 80% is NBD but best to size so that is relatively rare.

I find the "total Ah throughput" idea to be academic, in the real world longevity is cycles.

Of course if your rig simply can't carry the extra dead lead, then your choice becomes replace every two/few years, which is a valid choice,

or upgrade to LFP.

 

[steffen707]

The first step in an electrical system is to make a rough budget for AHs or watt-hours. This means a tally of all the consumers, their real world current or watt consumption, and then how often they are used. Do the same for charging if available. From there you can start refining whats possible.

i'll give a good look at my consumption figures

Once in a while hitting 80% is NBD but best to size so that is relatively rare.

I find the "total Ah throughput" idea to be academic, in the real world longevity is cycles.

Of course if your rig simply can't carry the extra dead lead, then your choice becomes replace every two/few years, which is a valid choice,

or upgrade to LFP.

ideally I wouldn't have $150 lbs of battery in the truck bed, LFP would be much more expensive know.

 

[rayra]

I'm running some smaller power tools off an inexpensive 1000W inverter in teh back of my Sub, from a solenoid-isolated Aux battery under the hood, with a pair of 1/0 cables run to the rear of the vehicle primarily so I can power a winch from the rear hitch. But as long as I was running those cables I'm using them as a power bus for just about everything else under the sun, including backfeeding the Aux from rooftop solar and charger-controller. I've got added fuse panel, 5VDC usb ports, 12VDC, cig lighter power ports, 12VDC Anderson power plugs, voltmeter, etc. all running in a smallish 'mondule' that's part of my rear storage drawers / platform.
I like options. Lots of options. Too, when messing with electric, thinking about the least gauge of wire you can get away with is 180deg wrong. Bump the size up for safety margin. Bump it up the most current you will likely flow. It migh tkeep you from burning your vehicle down later.

/ooh, I'm woozy, I just channeled Verkstad

 

[luthj]

If you plan to use the engine when powering large loads, then you just need enough battery to handle your smaller items. Fridge, lights, etc. You need to define your usage case though. 1-2 days weekend camping? Multi week trips? Then you can asses charging.

You may just need a 100AH aux battery and a good alternator charge connection. Plus solar, shore power charging or similar.

 

[steffen707]

If you plan to use the engine when powering large loads, then you just need enough battery to handle your smaller items. Fridge, lights, etc. You need to define your usage case though. 1-2 days weekend camping? Multi week trips? Then you can asses charging.

You may just need a 100AH aux battery and a good alternator charge connection. Plus solar, shore power charging or similar.

i'm looking into your suggestion now. Thanks!

 

[ducktapeguy]

For large loads you might want to look at under hood engine driven generators like what contractors use and downsize the inverter for smaller loads.

 

[steffen707]

For large loads you might want to look at under hood engine driven generators like what contractors use and downsize the inverter for smaller loads.

ohh, i've never heard of that. i'll take a peak.

 

[john61ct]

For large loads you might want to look at under hood engine driven generators like what contractors us.

Links to examples?

I've seen 15kW alternator setups, but they only output DC, still require big inverters.

 

[ducktapeguy]

Links to examples?

I've seen 15kW alternator setups, but they only output DC, still require big inverters.

Looks like most of the businesses that used to make them are no longer around, I can only find some references to them in old articles. I'm guessing the popularity of inverter based generators probably killed demand for them. They were essentially genset heads mounted in the engine compartment marketed for contractors and construction.

https://www.concreteconstruction.net/products/selecting-a-vehicle-mounted-generator_o

https://www.fabcopower.com/generat/bgen.htm

For the kind of power the OP is looking for I think a small generator would work best, I would be hesitant to put that kind of load on the stock alternator.

 

[john61ct]

Yes, a heavy duty e.g. Leece-Neville designed for emergency vehicles will do much better. 200A rating is the actual **continuous** output rating not as usual just the peak short time maximum.

 

[steffen707]

Is a 200amp still "small"?

 

[shade]

Is a 200amp still "small"?

There are small & large frame/case alternators.

No matter their rating, most automotive alternators are small frame, light duty cycle models. They'll either self-regulate to reduce output to save themselves from destruction, or they'll output all that they can until they die. DC-DC chargers can help manage the load to protect an alternator while still getting an acceptable output from it.

Here's a 200A continuous duty, large frame option: https://shop.marinehowto.com/products/cmi-200a-large-frame-j180-mount-extreme-duty-alternator

Here are some other high duty cycle options: https://shop.marinehowto.com/t/alternators--regulators

I'm not suggesting you replace or add a second alternator, though.

 

[luthj]

Note that marine alternators are designed/sized to run in hot engine compartments when temperatures can exceed 200° . typical automotive alternators do not need to run at temps that high.

 

[shade]

Note that marine alternators are designed/sized to run in hot engine compartments when temperatures can exceed 200° . typical automotive alternators do not need to run at temps that high.

Or for long periods to charge a large battery bank. I think it'd take a special use case to justify mounting one of those on most road going vehicles. Not many people travel with a 1000Ah LFP battery that gets heavily cycled.