Ram Promaster Forum banner

1 - 11 of 11 Posts

·
Premium Member
Joined
·
50 Posts
Discussion Starter · #1 · (Edited)
About to invest in batteries for my simple camper build and there has been tons of great discussion here on the topic. Anyway I found a great discussion (see link below) related to depth of discharge(DOD) and how too much discharge can wreak havoc on the the best batteries. I am afraid I have really discharged and killed batteries on past vans by just being ignorant on this! Anyway I was pretty interested to discover - and please comment if you disagree - that a 100 amp hour rated battery may realistically be only a 50 amp hour battery if you take it to only 50% discharge (which extends the battery life a lot!). According to the link below, 12.3 or so volts is the cutoff for 50%. So anyway, interested in comments on this...

https://deepcyclebatterystore.com/how-to-maintain-batteries/

Given I will invest in two 100 ah battery it seems I should buy either a quality Victron battery monitor (BMV 700 as per Gary's recommendation or the "smart" BMV 712 monitor - $150 to $200 depending on model) OR a Victron Battery Protect (model BP 65, $50) that isolates the battery at a specified low voltage. Comments welcome.

(In my case the load are modest (biggest loads being a 45qt dometic cooler in summer, and propex heater/LEDS in winter). Power supply will be two 100 watt or a single 280 watt PV module with MPPT controller, and the basic alternator back-up via isolator as per the PM forum))
 

·
Premium Member
Joined
·
8,836 Posts
Others will spend your money. I’ll take the other side. Until I got curious I had no battery monitor except the full charged light on my Tracer MPPT solar controller which blinks when the battery is fully charged. I paid a total of $170 for two Sams Club FLA golf cart batteries 215 A-H. Instead of spending $$$ on fancy other stuff I bought 200 watts of solar and a good controller and that is it ~$(350?) I didn’t really need to have any meter and still don’t even though I bought one for curiosity. I have way more electrical use than you plan. I use 325 Watt hours overnight (about 27 A-H) with a Norcold NR 751 refrigerator which must use twice yours, lights, Espar heater, Fantastic Vent, computer chargers, phone chargers, video, etc. At that rate I’d be at 50% sometime in the 4th day if the sun didn’t shine at all. I don’t need a meter to tell me it’s been dark or raining for 3 days and I need to start the van and switch my interconnection on. Go for Ice Cream or Coffee or a breakfast at Micki D’s perhaps. Save your money, Solar is magic, buy a little $20 watt meter if you must for satisfying your curiosity. If you must have the power going in and coming out of your battery buy two. But NONE is enough.
[ame]https://www.amazon.com/bayite-6-5-100V-Display-Multimeter-Voltmeter/dp/B013PKYILS/ref=sr_1_18?ie=UTF8&qid=1515459874&sr=8-18&keywords=Watt+meter[/ame]
 

·
Registered
2014 136” HR
Joined
·
5,803 Posts
OP, would you feel comfortable with only an idiot light on the dash instead of a fuel gauge and that light only comes on when the tank is full?

I can't speak to the options you mention--I've been very happy with my Trimetric 2030 from Bogart Engineering, and with Bogart themselves--but I will say that especially if you are new to this, it's really hard to develop an understanding of what is going on if you don't know what is going on.
 

·
Registered
Joined
·
538 Posts
I use a Chinese made 40 amp mppt controller I got off EBay. Works well. Doesn't track used wattage or anything fancy. But it has a nice volt meter for the batteries. Lets me know if it is charging or stopped. Allows me to set the peak charge voltage. And it has a USB charging port that works right up til sunset. I have found it easy to use and live with the past couple years.
 

·
Premium Member
2014, 138WB, High Roof, Gas, SW MT
Joined
·
2,112 Posts
hi,

I agree with RD that the monitor is not a necessity. It is a nice to have, and on trips I'll look at it at least a couple times a day.

I think that for on the road, a simple volt meter is kind of a minimum ($10) -- coupled with one of the charts that show battery state of charge vs voltage it gives a very rough idea when you are getting in trouble.
http://www.mmbalmainauto.com.au/PDF/State_of_charge_12_volt_batteries.pdf
Not perfect since battery has to be at rest for a while before voltage gives accurate state of charge, but helpful.

If you do get a monitor, it seems like the low voltage cutoff would be a worthwhile feature if it does not add a lot of expense.

The one that RD showed the listing for appears to only measure current in one direction, so it would not give you the net of charge + discharge, only the discharge -- unless you used two of them.

I've never had an occasion on the road when the house battery got dangerously low (below 20% SOC) -- the two times when I nearly totaled my batteries the RV was sitting in the driveway and I did not clear snow off the PV panels and the battery just got lower and lower from the small parasitic drains and self discharge.

If you look at the cylces vs depth of discharge that Trojan publishes for their batteries, they say that their golf cart battery is good for about 1250 cylces to 50% or 750 cycles to 80% depth of discharge. When you look at the way most RVs are used if you really got this kinds of cycle life, the batteries would last for a long long time. For example 50 nights a year to 80% depth of discharge would give you 750/50 = 15 years. Since people only get about 4 or 5 years out of a set of batteries, the batteries are dying of something else?

Gary
 

·
Premium Member
Joined
·
644 Posts
Others will spend your money. I’ll take the other side. Until I got curious I had no battery monitor except the full charged light on my Tracer MPPT solar controller which blinks when the battery is fully charged. I paid a total of $170 for two Sams Club FLA golf cart batteries 215 A-H. Instead of spending $$$ on fancy other stuff I bought 200 watts of solar and a good controller and that is it ~$(350?) I didn’t really need to have any meter and still don’t even though I bought one for curiosity. I have way more electrical use than you plan. I use 325 Watt hours overnight (about 27 A-H) with a Norcold NR 751 refrigerator which must use twice yours, lights, Espar heater, Fantastic Vent, computer chargers, phone chargers, video, etc. At that rate I’d be at 50% sometime in the 4th day if the sun didn’t shine at all. I don’t need a meter to tell me it’s been dark or raining for 3 days and I need to start the van and switch my interconnection on. Go for Ice Cream or Coffee or a breakfast at Micki D’s perhaps. Save your money, Solar is magic, buy a little $20 watt meter if you must for satisfying your curiosity. If you must have the power going in and coming out of your battery buy two. But NONE is enough.
https://www.amazon.com/bayite-6-5-1...F8&qid=1515459874&sr=8-18&keywords=Watt+meter
Just an FYI about those 100a meters, they come from the factory uncalibrated and voltage is often off by a lot. If you've got LA batteries, a voltmeter is often enough along with a chart with the corresponding estimated SOC. Lithium is another animal entirely since they have a flat discharge curve. 12.8v could be 90% full or 20% full and a matter monitor with current sensor is a must.

Slightly more expensive, but is multidirectional (EDIT: can't detect current at the same time, so basically useless) and up to 100a:

[ame]https://www.amazon.com/DROK-Multimeter-Voltmeter-Capacity-Charge-Discharge/dp/B01M5CWR2P/ref=pd_sim_263_3?_encoding=UTF8&pd_rd_i=B01MZIAJI0&pd_rd_r=JXYT4CJANX7KNKBS2X32&pd_rd_w=MnNe3&pd_rd_wg=ffxjX&refRID=JXYT4CJANX7KNKBS2X32&th=1[/ame]
 

·
Registered
Joined
·
808 Posts
Slightly more expensive, but is multidirectional (EDIT: can't detect current at the same time, so basically useless) and up to 100a:

https://www.amazon.com/DROK-Multime..._rd_wg=ffxjX&refRID=JXYT4CJANX7KNKBS2X32&th=1
I see this one has a Hall effect option. Might be a little OT, but does anyone own a clamp meter that measures DC current? I'm not so interested in measuring the state of the battery, but general measurements and troubleshooting. I've never owned one, so I'm wondering if they are any good and if there are relatively cheap adequate meters available.
 

·
Registered
Joined
·
127 Posts
clamp meters are great tools... for general measurements and troubleshooting though, i'd get a decent multimeter first, if you don't have one.
 

·
Registered
Joined
·
413 Posts
hi,



The one that RD showed the listing for appears to only measure current in one direction, so it would not give you the net of charge + discharge, only the discharge -- unless you used two of them.



Gary
The wiring instructions for these 100a meters, such as the one RD and others have shown, seem to indicate that with the shunt attached to the battery, the meter will display zero charging current when the battery is discharging and will display zero discharging current when the battery is charging. So even if you have 2 meters you may not get full data. I have a couple of these meters but have so far only hooked one up. I wired it to show discharging current while testing a microwave. It correctly provided discharging current when running the microwave without the engine running. Since I was getting poor performance from the microwave, I decided to start the engine to boost the batteries. The microwave now performed well but since the battery was now receiving a charge from the alternator, the discharge current went to zero.

Adding a second meter shouldn't change that because the second meter would be to measure current in the other direction.

So if this is true, then during the day when receiving charging current from solar panels,or while driving connected to alternator or charger, the discharge current displayed would be zero. And anytime that a load is running, i.e. lights, refrigerator cycled on, phone/laptop charging, etc., then the charging meter would display zero incoming current.

On the other hand, the wiring diagram shows if the shunt is between the solar panel and the charge controller, or between the charge controller and a connected load, this zero data reading situation does not occur. However this seems to indicate that the shunt between the solar panel and charge controller measures current produced by the solar panel, whereas the shunt attached to the battery will measure current flowing into the battery. If I understand it correctly these might not be the same since a fully charged battery will not accept all the current that a solar panel will produce.

Has anyone using these meters had a different experience?
 

Attachments

·
Premium Member
2014, 138WB, High Roof, Gas, SW MT
Joined
·
2,112 Posts
I see this one has a Hall effect option. Might be a little OT, but does anyone own a clamp meter that measures DC current? I'm not so interested in measuring the state of the battery, but general measurements and troubleshooting. I've never owned one, so I'm wondering if they are any good and if there are relatively cheap adequate meters available.
Hi,
I have the Klein CL2000. I bought it because it does do clamp on DC current readings -- the clamp on I had before only did AC.
Very nice meter with a lot of little convenience features.
Does a good job with the DC current clamp on readings.

Gary
 
1 - 11 of 11 Posts
Top