Waterproof Digital Voltmeter by ADvmonster

[hyperboarder]

Originally Posted by sanjoh

Did you get it installed?

I did, it's not the prettiest (cut the dash and siliconed it in), but it's working great. I'll post a pic someday...

[Sparrowhawk]

Originally Posted by sanjoh

2% of full scale (28v) or about .5 volts.

Thanks. That's fine for lead/acid but won't work for anybody using the newer LiFePO4 batteries. They have a very flat voltage curve as the battery discharges. A half a volt could be the difference between fully charged and a battery dead beyond recovery.

[mrt10x]

Originally Posted by Sparrowhawk

Thanks. That's fine for lead/acid but won't work for anybody using the newer LiFePO4 batteries. They have a very flat voltage curve as the battery discharges. A half a volt could be the difference between fully charged and a battery dead beyond recovery.

So are you saying this is not good for those of us running Shorai batteries?

[sanjoh]

Originally Posted by Sparrowhawk

Thanks. That's fine for lead/acid but won't work for anybody using the newer LiFePO4 batteries. They have a very flat voltage curve as the battery discharges. A half a volt could be the difference between fully charged and a battery dead beyond recovery.

That's a good point, however if you are into the area where the battery is loosing voltage rapidly, the battery protection circuit should have a LVC(low voltage cutoff). If your lithium chemistry battery does not have a LVC, you will be stranded, maybe not today but eventually. Once the Lithium battery voltage is below the minimum voltage per cell, the chemistry is done, there is no resurrection or shocking like a nicad.

Originally Posted by mrt10x

So are you saying this is not good for those of us running Shorai batteries?

The meter will work fine for monitoring your battery and charging system.

With my years of working in measurement, I assumed the voltmeter was like most others with respect to accuracy, it is not.

The accuracy of the voltmeter is +0.3% of full scale or +0.084v from actual reading.

[Sparrowhawk]

Originally Posted by sanjoh

That's a good point, however if you are into the area where the battery is loosing voltage rapidly, the battery protection circuit should have a LVC(low voltage cutoff). If your lithium chemistry battery does not have a LVC, you will be stranded, maybe not today but eventually. Once the Lithium battery voltage is below the minimum voltage per cell, the chemistry is done, there is no resurrection or shocking like a nicad.

.............

The meter will work fine for monitoring your battery and charging system.

With my years of working in measurement, I assumed the voltmeter was like most others with respect to accuracy, it is not.

The accuracy of the voltmeter is +0.3% of full scale or +0.084v from actual reading.

A meter like this will be sufficient to tell you if your charging system is working at a high enough level to charge the battery (AOK or too many accessories on at the same time or charging system failure). It won't be able to let you know the state of charge of a Shorai or other LiPO4Fe battery with the engine turned off.

As lead/acid batteries discharge they decrease in voltage from over 13 fully charged to below 11 when they are getting low. Most volt meters, this one included, will give you an idea of a low conventional battery state of charge if you left something on or let it sit for months without a trickle. LiPO4Fe batteries remain near full voltage until they discharge enough to be permanently damaged.

It's not really a deficiency of this meter. It requires an expensive, high accuracy volt meter to use for that purpose. It's just a trait of the LiPO4Fe battery that a person needs to be aware of so you know what information a voltage reading is and is not telling you. You simply have to understand that a good volt reading off the battery doesn't mean the battery is fully charged.

[sanjoh]

Originally Posted by Sparrowhawk

It won't be able to let you know the state of charge of a Shorai or other LiPO4Fe battery with the engine turned off.

Rather than focus on opinion, I prefer to deal with facts.

This is a chart from the Shorai website FAQ


Quoted from Shorai "If you are storing your vehicle and want to check the remaining capacity, or you're a racer with a constant-loss system, you'll want to know how resting voltage (i.e. with no load or load under 200mA) maps to remaining capacity. LFX batteries should be maintained such that 20% capacity remains at minimum, as best practice. Use a good-quality voltmeter to check remaining capacity, and consider recharge whenever the battery capacity falls to about 50% remaining"

Shorai reccommends charging when capacity reaches 50% or 13.116v, while the minimum voltage (20% capacity) is 12.866v, a difference of .25v (13.116-12.866). ANY voltmeter used to check the voltage on these batteries must have an accuracy of at least .25v.

The accuracy of this meter at +0.084v is near 3x more accurate than needed to detetermine the state of charge of a Shorai battery.

Clearly this meter is capable

[sanjoh]

Woohoo, XT225 Install

[Sparrowhawk]

Originally Posted by Sparrowhawk

What is the actual accuracy of the unit?

Originally Posted by sanjoh

2% of full scale (28v) or about .5 volts.

Originally Posted by sanjoh

Rather than focus on opinion, I prefer to deal with facts.

This is a chart from the Shorai website FAQ


The accuracy of this meter at +0.084v is near 3x more accurate than needed to detetermine the state of charge of a Shorai battery.

Clearly this meter is capable

Most of us prefer to deal with facts. It just gets tricky when the facts keep changing.

I didn't mean to pee on your product (it's waterproof so won't hurt it anyway) but when I asked about accuracy you responded with 2% or 0.5v. Now it's 0.084v.

It doesn't matter to me either way but it's good to know what any instrument is, and is not, capable of telling you. From the chart above, +/-0.5v would not differentiate between a Shorai with 70% charge and one that had been killed by discharging to less than 10%.

[sanjoh]

What you are looking for is not here, please move along.

IF you follow the manufacturers guidelines, the meter is more than adequate as was pointed out.

[Sparrowhawk]

Originally Posted by sanjoh

What you are looking for is not here, please move along.

I was looking for product specifications but I agree, they are not to be found here. I'll be moving along now.

[sanjoh]

Originally Posted by Sparrowhawk

I'll be moving along now.

Now that is funny, you actually thought I was referring to you

[Avner]

[Potosi Joe]

How about a pic of the XT showing the fairing.

Originally Posted by sanjoh

Woohoo, XT225 Install

[sanjoh]

Originally Posted by Potosi Joe

How about a pic of the XT showing the fairing.

See more pics here

[Potosi Joe]

Thanks for the pics. I think it looks awesome. A+ on your fairing. Thanks Joe

Originally Posted by sanjoh

See more pics here