Battery Monitor

[Toodie]

I would like to install a monitor on the battery for our 2005 SD. Anyone familiar with the DOC Wattson model R102 digital panel meter? If not, if you could recommend a good monitor, I'd really appreciate it.

Bill

[Bigfoot Mike]

I have seen several people prefer the “Xantrex Link-10” (Formerly the E-meter).





http://www.energyoutfitters.com/default.ht...rex_link10.shtm

Good Luck on your quest. Let us know & show us photos with what you come up with.

[Steve C.]

I use the Xantrex link 10, and highly recommended this device. It is so much more informative and more accurate than the simple led displays, for me, it is worth every penny of it's price.

Steve.

[Byron Kinnaman]

I'm wondering is the Xantrex link 10 is that much better than the DOC wattson. Check out the price here.. The DOC Wattson model R102 digital panel meter looks like a pretty good deal at $60.00 vs $300.00

[Bigfoot Mike]

I'm wondering is the Xantrex link 10 is that much better than the DOC wattson. Check out the price here.. The DOC Wattson model R102 digital panel meter looks like a pretty good deal at $60.00 vs $300.00

I agree, really spendy.

When I was posting that info, I was wondering the same thing. I decided I would just put the info out there.

I have a friend that has the Link 10 and thinks it is the way to go.

PS: I believe the sale price is $210.00

[Byron Kinnaman]

I agree, really spendy.

When I was posting that info, I was wondering the same thing. I decided I would just put the info out there.

I have a friend that has the Link 10 and thinks it is the way to go.

PS: I believe the sale price is $210.00

You're right about the price of $210.00. Add a shunt (it's necessary) $20.00. Add few other things, like mounting, wire, and shipping. Maybe not quite $300.00. Would be belive $250.00?

[Morgan]

I installed a Link 10 on a previous trailer and found it satisfactory. I bought mine from Camping World for $80 (including shunt and cable) when they were closing them out.

The Link 10 is more accurate in its computations than the R102, but I doubt it's worth four times as much. Looking at the specifications for the R102, I'd say it is accurate enough (at least for my use). Purists may prefer the Link 10.

I certainly would not have paid $200 to $300 for the Link 10.

Google found a place selling the Link 10 for $190 including the 500 amp shunt.

Link 10 for $190

[Steve L.]

At the time I bought my Link 10 almost 4 years ago I searched about first but the Link 10 was all I could find. This new meter seems attractive for the price and I suspect that the accuracy is good enough for our needs.

I presume it shows amperage in as well as amperage out and it isn't clear to me what the mounting options are.

[Joe MacDonald]

looking at the manual for the Doc Wattson meter, it seems it is configured as either a how much used, or a how much charged meter, but both states can't be checked without re-wiring fro discharge to charge monitoring.a bit of a pain if you want to see both, and keep track.

[Steve L.]

I suppose that is another nice thing about the Link 10, being able to track the actual amp hours back into the battery. The Link 10 will count up the amp hours as I use the battery, then count them down as I recharge on the generator. I use this display quite a bit when boondocking.

Using the meter I've observed the reefer drain and tow vehicle recharge capabilities on longer trips. My observations make me skeptical about some recharging claims while towing.

It's still an issue of balancing the relative costs of the two units in terms of the perceived benefit for the individual purchaser.

Given the embarrassing amount of money I've (and you?) spent looking for the perfect LED replacement for incandescent bulbs, I may not be a good role model. As my calender for the month of August claims, "It could be that the purpose of your(my) life is to serve as a warning to others."

[Morgan]

looking at the manual for the Doc Wattson meter, it seems it is configured as either a how much used, or a how much charged meter, but both states can't be checked without re-wiring fro discharge to charge monitoring.a bit of a pain if you want to see both, and keep track.

Good eye, Joe, I didn't catch that. I emailed them to ask if that is truly the case - I can't believe it. Well I can believe it; they are for radio controlled models which don't have on-board chargers.

If I hear from them, I'll post their reply here.

ON EDIT: Reading their FAQ, I found the answer to my question. The manual is correct, the meter will read current (and current derived values) in only one direction.

That pretty much renders it useless in an RV with a built-in automatic battery charger or a solar charger.

Makes $200 for the Link 10 look a bit better.

[Byron Kinnaman]

Good eye, Joe, I didn't catch that. I emailed them to ask if that is truly the case - I can't believe it. Well I can believe it; they are for radio controlled models which don't have on-board chargers.

If I hear from them, I'll post their reply here.

ON EDIT: Reading their FAQ, I found the answer to my question. The manual is correct, the meter will read current (and current derived values) in only one direction.

That pretty much renders it useless in an RV with a built-in automatic battery charger or a solar charger.

Makes $200 for the Link 10 look a bit better.

I think I'm missing something here. For me, at any rate, I want to know how much I've used. I think I can trust the battery charger and the TV to get the battery to a full charge without paying much attention to them. I can see a desire to know how much of the avaliable capacity you've used which would aid in knowing when to cut back on usage. So whats gained in knowing how much you've put back in?

[Dan Meyer]

I use an automotive voltmeter and amp meter to get an idea of what is going on with my battery. The following table (from www.batteryfaq.org) shows the capacity of a lead acid battery that is at rest at 80 degrees.

Volts / Charge
12.8 / 100 percent
12.6 / 75 percent
12.4 / 50 percent
12.0 / 25 percent
11.8 / 0 percent

I have found that even with a brand new connector on my trailer and tow vehicle, I can not get more than about a 7 amp charge to my trailer battery. This means that if you run your trailer battery flat it will take all day to charge it from your tow vehicle. In my opinion, depending upon your tow vehicle to charge your trailer's battery is a bad idea.

I also monitor outdoor temperature and water pressure. See pictures and a story about installing my monitoring panel at http://scamp.n0kfb.org/ - click on "modifications and repairs". and scroll down about 1/4 of the page.

-- Dan Meyer

[Morgan]

I think I'm missing something here. For me, at any rate, I want to know how much I've used. I think I can trust the battery charger and the TV to get the battery to a full charge without paying much attention to them. I can see a desire to know how much of the avaliable capacity you've used which would aid in knowing when to cut back on usage. So whats gained in knowing how much you've put back in?

Byron,

The state of charge of the battery depends on how many ampere-hours you've used versus how many ampere-hours you've put back in. Ampere-hours is just current (amperes) integrated over time.

If you start with a fully charged battery (say, 100 Ah) and withdraw 10 Ah then the charger replaces 5 Ah, you've run a deficit of 5 Ah. The battery now has 95 Ah of charge remaining.

If you have no charger hooked up to the battery, it makes no difference. There is no current going into the battery.

[Steve L.]

When camping for an extended time without an electrical hookup, I track amp-hours out.

Then at some point, I connect the Honda generator and run it long enough to get back to 70-80% full amp-hour capacity. About that time, most chargers are starting to ramp down the current anyhow. I get the most charge for the minimum generator time.

I like amp-hours because it's a (relatively) simple value for the meter to track and judging the charge state by voltage is tricky because of the wait time to get a stable voltage after any charge or drain load.

Now, if I were to completely surrender to the dark force, I'd spring for the optional battery temperature sensor since battery charge is temperature sensitive. Haven't been able to justify it. Yet.

[Byron Kinnaman]

Byron,

The state of charge of the battery depends on how many ampere-hours you've used versus how many ampere-hours you've put back in. Ampere-hours is just current (amperes) integrated over time.

If you start with a fully charged battery (say, 100 Ah) and withdraw 10 Ah then the charger replaces 5 Ah, you've run a deficit of 5 Ah. The battery now has 95 Ah of charge remaining.

If you have no charger hooked up to the battery, it makes no difference. There is no current going into the battery.

I understand all the electric stuff. (Byron's an electronic engineer) But I don't see where there's a need to monitor how many Amp hours are put back in, certainly not a $100 need. The only thing I can think of is if you are in the habit of partially charging your battery, but then you'd have to put a lot of time in understanding how your battery works to have any idea how much juice is left. I can see where it might be usefull for a short period of time to know how much you're using. But after a while that doesn't have a lot use either. You develope habits that allow you to do what's needed. Besides the amount of charge in a battery is at best an estimate. Temperature and battery age also play a part therefore any attempt to be exact isn't going to work.

[Curtis F.]

Can 2 DOC Wattson meters be wired in. One for discharge and one for charge?
Nah, it would get too complicated adding the value from one meter and subtracting the value from the other meter.

Curt

[Morgan]

Here's my question to RC Electronics and their reply:

You are correct that it only measures in one direction from LOAD to SOURCE.
The integral of charge in and charge out of a Lead-acid battery is seldom zero. Hence any such system requires various assumptions and corrections to provide a reasonably accurate result. The low cost and simplicity of this meter rule against that. You're better off with two meters back to back.
Best regards,
-Keith

At 08:39 AM 8/1/2006, you wrote:

Your specifications and your manual (particularly the connection diagrams) indicate that the meter will measure current (and charge) in only one direction.

If the meter is wired between the battery and the load and if a battery charger is on the load side of the meter, will the meter measure the charge as well as the discharge? An RV or a boat would have such a circuit (so does a car or truck) and the charging would be done automatically by the charger.

If the specifications are correct and the meter only measures 0-100 amperes rather than plus or minus 50 amperes, the meter would be of little use in such a circuit.

Thanks,
Morgan