Need the solar/power pros to weigh in

[TantoTrailers]

Understood, the trip is 2 nights and basically a cold weather shakedown and a chance to test out some of the new gear like the DC/DC converter, insulation in the floor, and a new heat source for the cabin. Would I be doing the battery a disservice by using it after 18h of charging or would that not be a problem at all? I suppose it will also get some charge during the drive but that converter won’t be tweaked at all.

regarding the battery capacity test, I should be showing close to 100ah consumed if I run it down to 10v right? Not that I’m going to I’m just trying to better understand the capacity measurements.
^Im going to call this a dumb question and based on the previous responses you guys posted the answer is yes.

 

[dreadlocks]

your good to go, you just want it charged fully because its probably not after sitting on shelf.. and you needa calibrate your BMV

The BMV does its best to calculate what the battery's true SOC is, it does this by measuring how much you take out/put in after telling it its completely full (calibration).. it tries to calculate losses and stuff but it can vary a bit but overall it will be consistent in telling you how much you've taken out.

Keep an eye on its SOC and try to not let it get much below say 50% if you can, if you want later you can put a Battery Protect in and have it drop your loads automatically if battery starts to become too deeply discharged..

when you get home put it back on the charger, I dont like leaving em on chargers all the time.. if you get a nice timer you can have it come on for a few hours a week, or even daily and its a bit more safe on the battery than just a constant charge for weeks on end non stop.

 

[TantoTrailers]

your good to go, you just want it charged fully because its probably not after sitting on shelf.. and you needa calibrate your BMV

The BMV does its best to calculate what the battery's true SOC is, it does this by measuring how much you take out/put in after telling it its completely full (calibration).. it tries to calculate losses and stuff but it can vary a bit but overall it will be consistent in telling you how much you've taken out.

Keep an eye on its SOC and try to not let it get much below say 50% if you can, if you want later you can put a Battery Protect in and have it drop your loads automatically if battery starts to become too deeply discharged..

when you get home put it back on the charger, I dont like leaving em on chargers all the time.. if you get a nice timer you can have it come on for a few hours a week, or even a day and its a bit more safe on the battery than just a constant charge for weeks on end non stop.

I was going to ask how to have the load auto dropped if the voltage drops below a certain level...the battery protect is what I’m after. Xmas list! For now I will monitor diligently. The IP67 is mounted inside so I will be able to charge at camp (and hopefully while driving if the converter works!). I have some WiFi outlets that I can program on a schedule (maybe 8 hrs every Wednesday) so that’s probably going to be my game plan for garage storage but the camper will see monthly use all year regardless. thank you for the brain dumps!

Something like this for the protect?

Victron Energy BPR065022000 Smart BatteryProtect with Bluetooth 12/24V - 65A

Victron Energy BP65 Smart BatteryProtect with Bluetooth 12/24V - 65A

shop.pkys.com

 

[dreadlocks]

you can also wire the relay output from the BMV to the remote IO input on the Battery Protect, this will let you have the BMV Drop loads based off Calculated SOC (and other params)

the way I have mine setup is the Low Voltage Disconnect is above full depletion but not high enough to get triggered by a heavy short load, like a jump start or something.. but low SOC Disconnect based on calculated value higher than the LVD would see.. I have a switch wired up in parallel with the BMV that can over-ride the BMV and turn the Battery Protect back on.. I call this my Reserve Capacity switch, for a FLA/AGM I'd have the LVD set at ~35% SOC and the BMV set to 50% SOC, and if the BMV drops all loads and I really need more power, I'd flip the reserve switch and have another ~15% capacity until the LVD kicks in and saves the battery from turning into a paper weight.. Hopefully dont ever need to use reserve capacity, but if you need too you can access it manually.. knowing the repercussions of mebe loosing a few cycles in exchange for getting through a desperately cold night.

 

[luthj]

Generally speaking I prefer to leave lead batteries on a float charger when not in service. An exception would be batteries that get topped up every month or so, or batteries stored in cold conditions.

There are generally two float voltage levels. Batteries regularly cycled should have the higher float voltage, to encourage true 100% charging between cycles. Batteries that are used for back (100% float service) should have a lower float voltage. For those types of applications, grid corrosion caused by the higher float voltage is more of a concern than recovering from a deep discharge, and reducing sulfation.

 

[dwh]

Capacity test depends on load. Deep cycle lead-acid batteries' capacity is rated based on load. For example, @10hr rate, @20hr rate, etc.

So to test the 20hr rate, for say a battery rated "100ah@20hr rate", you would use a 5a load, which should test out to about 20hr/100ah.

Due to Peukert's law, if you doubled the load to test 10hr rate, you would get somewhere less than 100ah. Halve the load, you'll get more than 100ah.

Since it varies, just running the battery down without carefully controlling the load, then recharging and reading the meter to see how many amp hours went back in, will get you a ballpark number, but it could still be quite a bit off.

 

[TantoTrailers]

you can also wire the relay output from the BMV to the remote IO input on the Battery Protect, this will let you have the BMV Drop loads based off Calculated SOC (and other params)

the way I have mine setup is the Low Voltage Disconnect is above full depletion but not high enough to get triggered by a heavy short load, like a jump start or something.. but low SOC Disconnect based on calculated value higher than the LVD would see.. I have a switch wired up in parallel with the BMV that can over-ride the BMV and turn the Battery Protect back on.. I call this my Reserve Capacity switch, for a FLA/AGM I'd have the LVD set at ~35% SOC and the BMV set to 50% SOC, and if the BMV drops all loads and I really need more power, I'd flip the reserve switch and have another ~15% capacity until the LVD kicks in and saves the battery from turning into a paper weight.. Hopefully dont ever need to use reserve capacity, but if you need too you can access it manually.. knowing the repercussions of mebe loosing a few cycles in exchange for getting through a desperately cold night.

AHH another brain dump, this one I will need to read several time!

Capacity test depends on load. Deep cycle lead-acid batteries' capacity is rated based on load. For example, @10hr rate, @20hr rate, etc.

So to test the 20hr rate, for say a battery rated "100ah@20hr rate", you would use a 5a load, which should test out to about 20hr/100ah.

Due to Peukert's law, if you doubled the load to test 10hr rate, you would get somewhere less than 100ah. Halve the load, you'll get more than 100ah.

Since it varies, just running the battery down without carefully controlling the load, then recharging and reading the meter to see how many amp hours went back in, will get you a ballpark number, but it could still be quite a bit off.

^This is very helpful thank you for the clear explanation, I had no idea what the 10/20Hr rate thing meant.

BTW, Sams Duracell special is sitting in the truck ready to pop in the toaster! I didnt think about it but strapping this thing down will be a PITA as the terminals and handle are in the center on top where my strap went on the old battery......hooooooops for days over here.

Any point in getting bluetooth on the battery protect? Seems kinda basic in the demo mode...option to turn the load off which I don't think I would ever use.

 

[shade]

Any point in getting bluetooth on the battery protect? Seems kinda basic in the demo mode...option to turn the load off which I don't think I would ever use.

No, but yes?

I didn't need BT for my system, and the dumb ones cost a little less, but I decided to go smart in case Victron dreams up some new use for the BT function that I'd regret not having. Unlikely, but possible.

 

[dreadlocks]

The Bluetooth one lets you set custom setpoints, however for a lead battery the default set points are pretty suitable.. and if you wire it up to be controlled by the BMV you can adjust voltage there if you dont like the dumb ones..

 

[TantoTrailers]

I reckon its cheap enough difference that it makes sense to just get the bluetooth for futureproofing! Probably should have bought it before the battery hahaha but I will be diligent till I have it.

 

[dreadlocks]

I'm a strong advocate for the Battery Protect, custom set points in a standalone unit thats solid state and does not become a parasitic drain all on its own.. really hard to beat such a good whole system LVD, a decade ago I was building em by hand and just the solid state DC relay cost more than these do, and I had a bunch of external circuitry that made it look like a hodgepodge.

Wire all the charge inputs directly to the battery, or at least on input side of BP, dont try to push current backwards through it.. you also want it to recover the voltage and reconnect your loads when the battery is given a charge current.

 

[TantoTrailers]

I gotcha, I was thinking of just basically putting it on the wire that goes from the battery to my fuse box with an inline fuse between BP and battery. Every charge input is directly on the battery terminal.

 

[dreadlocks]

If it has a bolt style terminal on the battery I'm really fond of using these terminal fuses: https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

Also check out this if you havent: http://circuitwizard.bluesea.com/

Ive got a 200A main fuse on mine, which is twice as much as I need nominally, but half of what the main bus wiring can support before it starts getting all smokey.. so it should not ever pop on me unless something's gone terribly wrong.. and 200A is my battery's max intermittent rating.

 

[TantoTrailers]

Ill take a look at those. Got my multimeter on the battery and its sitting at 12.83V from the store.

 

[dreadlocks]

thats a great reading fresh from the store, should be mostly charged..