Ideas for charging the batteries in an Oshkosk M1070

[Castle Bravo]

Something that helps to keep in mind when dealing with 4 battery military vehicle 12v/24v arrangements.

There are 8 battery posts among 4 batteries - 2 of these posts are 24v positive, 2 are ground, and the remaining 4 are 12v positive.

 

[slogutis]

Something that helps to keep in mind when dealing with 4 battery military vehicle 12v/24v arrangements.

There are 8 battery posts among 4 batteries - 2 of these posts are 24v positive, 2 are ground, and the remaining 4 are 12v positive.

Yes, I find it confusing. I have trouble determining whether to connect chargers/maintainers to those posts you describe or to just concentrate on the two separate linked batteries. I see you have an M1070, how do you keep your truck charged?

 

[74M35A2]

Lowest confusion method is to just charge each battery by itself with an automatic 12v charger. Don't have to disco (disconnect) anything. Two will show a long charge time, and two will show short charge times. When charger is done, move to next battery.

Nonetheless, this is the easiest way. If this does not work for you, you're doomed.

 

[slogutis]

Lowest confusion method is to just charge each battery by itself with an automatic 12v charger. Don't have to disco (disconnect) anything. Two will show a long charge time, and two will show short charge times. When charger is done, move to next battery.

Nonetheless, this is the easiest way. If this does not work for you, you're doomed.

Haha, I don't like the sound of that. However, learning I can charge each battery separately without disconnecting the whole harness makes me happy. I ordered up a couple solargizer to help keep the batteries topped off and make sure I don't get stranded somewhere. Since that's what caused this whole situation in the first place. I've also replaced one bad battery already and hope to replace the others as they become available. With all these corrections and precautions, I hope to be in good shape for the future.

 

[74M35A2]

My personal opinion, I don't know why people charge. It mostly stems from one wanting to keep the original mil batteries for whatever reason. If they are 5 years old or more, they are shot anyway, even if they are able to start the truck. Go with 4 new semi-truck group 31's, make sure your charging system works properly, there are no electrical draws when off, and you should never need to jump or charge it. I let my MV sit all winter, and it cranked perfectly this spring without ever touching it in storage. Charger is good for a car show or something where you want to run lights but not the engine all day, but for normal use, I threw my 24v charger away because I was sick of tripping over it.

I know this is going to be followed by people stating their Hawker's are 7 years old and still going strong and all that, and great, but the best way to do quantify it is to use a modern hand held tester that measures the battery internal resistance, and calculates the CCA power remaining of the battery. This is independent of charge level, and is not a load test. These work great to see where you are really at. If you want to do a simplistic load test, the vehicle itself works great, because it is a load. Disable the engine from starting, and crank the starter for up to 10 seconds, battery voltage should not drop below 20.0V. If it does, the batteries are weak, either charge level or total power holding capacity.

But honestly, if you ask anybody that upgraded to new commercial batteries and has a properly working charging system, there is no reason they should need a battery charger. It is just easier and works.

 

[slogutis]

Yeah, during my research of the truck I learned that they had draw issues. I plan to install a battery master switch, but being as the battery box is outside the vehicle i'm not sure how or where to place it. The gentleman I purchased the truck from replaced all 4 batteries with new Napa 6tls three years ago, but when I contacted Napa they said those batteries were discontinued due to short life span. So, just replacing the batteries may make all the difference I need but I want to make sure I do everything possible to keep it in good, reliable working order. Luckily I have my ever so reliable M932 that I have been able to slave jump from and rescued the M1070 when it wouldn't start after an hours drive away.